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Eastern Chipmunks Love Acorns

Driving down my road I occasionally see these little creatures shoot across with tails held straight up. These are Eastern Chipmunks.

Both chipmunks and ground squirrels live in Missouri. The ground squirrels are bigger with different coloring and don’t seem to live in my valley.

Except for an occasional sighting chipmunks aren’t noticed much either. My cats catch those that move into the yard. Their favorite routine is to bring the chipmunk into the house and let it go.

Cats do have a sense of humor and must enjoy watching me try to corner a terrified little rodent, scoot it into a container kept ready for such emergencies and slam the lid on. The chipmunk is then carried off down the road beyond where the cats normally go and turned loose.

eastern chipmunk
Eastern chipmunks give another meaning to cheeky. This one stashed an acorn in a cheek pouch for a secure carry back across the road. The swelling might give the impression of a big tumor, but it’s easily removed.

For some reason I had believed eastern chipmunks, like woodchucks, hibernated during the winter. So I was surprised to see several of them busy gathering acorns on a walk down the road.

Chipmunks do not hibernate. They do stay home in their burrows in cold weather. This means they must gather up a supply of food to snack on. Acorns are popular snacks.

That is exactly what these busy creatures were doing when I noticed them. It was hard to not notice one of them.

Most wildlife wants to avoid people. The birds keep flying off to a tree further down the road. Deer bound off white tails waving. Squirrels streak up the trees.

eastern chipmunk eating acorn
Being a rodent, the front gnawing teeth have enamel only on the front which grows continuously. Gnawing on things like acorns wears it away and keeps it razor sharp. The fingers are long on all four paws and have good nails for digging burrows. What most people see is how cute they are.

Eastern chipmunks often do take off and are only rustling in the leaves. One was determined to get another acorn. It darted across the road about ten feet in front of me, stuffed two acorns in its cheek pouches, sat on a fallen branch to assess what I was up to and darted back across the road.

The little rodent didn’t go far. It raced up a fallen tree and across to a perch on another fallen branch to eat an acorn. I assume it was the same one. I saw two or three others in the area.

The next morning was twenty-five degrees. It warmed up quickly and I went walking. The chipmunks had all stayed in their burrows.

Fall Into Winter Begins

Nature really has only two seasons in the Ozarks. One is growing season. The other is winter. Now the Ozarks is waiting to fall into winter.

Most plants still look green. Looking carefully there is a yellow cast hiding under that green. The few cold nights have turned some plants like the dogwoods to fall colors.

fall into winter foliage and color
Leaves are turning red as sunflowers and asters bloom. The growing season will continue until killing frost turns the plants black one morning.

Wait a minute. Isn’t fall another season? It is for people. For plants it is still part of the growing season as they busily make seeds and store sugars and starches down in their roots for the coming winter.

Green chlorophyll doesn’t photosynthesize well in cooler temperatures so the anthocyanins take over. These come in colors other than green.

For turkeys, deer, squirrels and other such creatures the fall into winter means an abundance of seeds and nuts to gather. They don’t care about colors in the leaves, only in eating and hiding enough of this bounty to survive the winter.

deer waiting to fall into winter coat
Still in the golden brown summer coat this young white tailed deer stands in a patch of sunlight along the road debating whether to flee. The notched ear indicates this one has had a close call in the past. She needs to learn to flee from people fast as hunting season opens soon.

The deer are putting on their dark brown winter coats. The raccoons are retiring up into the hills.

Birds are more mobile. Many of them are following the warmth south. One by one the hummingbird feeders are being cleaned and stored. Migrants are stopping by to stock up on sunflower seeds for extra energy giving us a chance to see some new birds.

The usual residents are ignoring the feeder as they load up on other delectables. This excepts the morning doves who leave standing room only on the feeder in the morning.

The turkey vultures are gathering and soaring in lazy circles as they drift south. The goldfinches have shed their gold feathers and are dull green now.

River oats
One of the easiest grasses to identify, the flat seed clumps are unique. At the end of the growing season they dangle glowing gold in the sun and tremble in the breeze.

The winter visitors haven’t arrived yet. These are the juncos, various sparrows and titmice.

The days are getting short. The temperatures are warm all day and cool at night. All it will take is a good rain and the Ozarks will fall into winter.

Meander through the seasons in photographs in “My Ozark Home.”

Shelf Mushroom Appear For Spring

Spring has arrived with rain and warmer temperatures. This brings out the shelf mushroom crops.

shelf mushroom on log
A storm several years ago knocked over this large tree down by the river. The road crew cut it up and rolled the pieces off the road and into the edge of the woods. Walking by I noticed the crop of shelf mushrooms. The fresh ones are light in color. As they age, they darken. All are tough.

There are many kinds of shelf mushrooms. They are not all in the same mushroom groups for many reasons. I’m not very knowledgeable about mushrooms so I tend to look at them the same way.

shelf mushroom from top
The size of the fan may vary. The thickness may vary. The edge may be smooth or ruffled. All shelf mushrooms are semicircles.

The shelf mushrooms I see are on dead or dying trees. They jut out with a half to two thirds circular shelf. Underneath is a stem joining the shelf to the tree.

gilled shelf mushroom
This shelf mushroom has gills under its cap.

Some of the shelves have gills under them. Others have pores that look like tiny holes under them. This is why they are split into different groups.

pored shelf mushroom
Under this shelf mushroom cap is a spongy surface of pores.

The shelves are different. Some are thick and woody. Some are thin. Some are in piles. Others are separate. Some are pink or blue or lined.

Size varies too. Some are barely an inch across. Others are small plates.

Some of these mushrooms are found only in particular seasons. Others can show up anytime after a nice, warm rain.

salmon shelf mushroom
I think this is a mound of salmon shelf mushrooms. They were on a tree stump. They are supposed to be edible, but I hesitated as I wasn’t positive of my identification.

People do eat some of the shelf mushrooms. Chicken of the Woods and Oyster Mushrooms are two of the favorites. These are fairly easy to identify definitely.

Some of these mushrooms are poisonous. Most are ones no one would want to eat due to bitter flavor or woody texture.

For myself, I don’t hunt for shelf mushrooms to eat. I browse through the mushroom guides and see that many of the edible ones are too easy to confuse with others listed as not edible.

pink shelf mushroom
The soft pink color seems to glow for these shelf mushrooms on a fallen log.

A trusted friend did give me some Chicken of the Woods once. This shelf mushroom can form huge piles of shelves. It was good. I don’t trust myself to identify it on my own.

Spring brings up many mushrooms much easier to identify. Another month brings morel season. That is one mushroom I can identify confidently.

Find out more about Ozark nature in “Exploring the Ozark Hills.”

Paradoxa Native Plant Walk

Sunday afternoon was a pleasant escape from cleaning up after six inches of rain with the high water that followed. Paradoxa, the Rolla chapter of the Missouri Native Plant Society, held a winter tree identification walk.

Finding trees is easy in the Ozarks. They tend to be big and hard to miss. Over the winter most trees are bare trunks and branches.

For someone like me who depends on leaves and flowers to identify a plant, bare trunks and branches are daunting. Where do you start?

tree barks

Bark helps identify a tree in winter. The Osage orange bark (left) is yellow with long ribbons intertwined. Shagbark hickory (center) has long, thin plates of grey bark. American elm (right) looks like well worn gray pavement.

As the Paradoxa group wandered around looking at the different trees, several important things to look for became obvious. First was bark.

All trees have bark. Take a closer look at the bark. Bark is not usually smooth and featureless. Bark has color, texture and furrow patterns. The combinations help identify the tree.

terminal tree buds

Terminal buds are another help in identifying a tree in winter. Osage orange (left) has small buds on a big bulge. Post oak buds (center) have shingled scales and a gang of buds. Shagbark hickory (right) has a single large bud with two scales, one on each side. This bud is starting to open.

A second characteristic is the terminal buds. When a tree goes dormant in the fall, it makes leaf buds covered by scales on its branches. The one on the tip of a branch or twig is the terminal bud.

Some buds have many small scales giving the bud a shingled look. Others have two scales, one on each side.

Some trees have a single terminal bud. Other trees like to have groups of buds.

Paradoxa plant group

Two retired forest service men led the Paradoxa group on their winter tree identification walk.

The Paradoxa group looked at the bark and buds. Some were easy like the black walnut. Others were hard.

Where do you go for the hard ones?

One place is the winter tree guide published by the Missouri Department of Conservation. The Missouri Trees guide has the bark and buds in it.

Paradoxa group hiking

The Paradoxa group includes people of all ages. Many are Master gardeners or naturalists. All are interested in Missouri native plants.

The more interesting place to go is on a guided walk like the one Paradoxa held on Sunday. Everyone on the walk is interested in Missouri plants. Each person knows a different set of plants.

As we walked along, we made comments about the different trees. Those who recognized the tree helped those who didn’t spot the best ways to identify it in the future.

The Missouri Native Plant Society has chapters like Paradoxa in many parts of Missouri. Anyone interested in Missouri plants will find joining the groups helpful and fun.

Yellow Ironweed Verbesina alternifolia

Yellow is the color of late summer in the Ozarks. Yellow Ironweed is one of the many yellow wildflowers blooming along the roads and in the pastures from august to killing frost.

 

Verbesina alternifolia Britton ex Kearney

August to October                                       N                                 Family: Asteraceae

                                                                                                            Tribe: Heliantheae

yellow ironweed flower

Flower: A profusion of yellow flowers top short stems forming a loose head at the top of the plant. Not all of the flowers bloom at the same time. Each flower head has up to 10 bright orange yellow ray flowers sweeping down from the globular mass of yellow tube flowers. These are up to half an inch long and stick out individually.

yellow ironweed side flower

Leaf: The leaves are usually alternate but may be opposite in part or all of the plant. The lower leaves may have a short, winged petiole but upper leaves are sessile. each leaf has a slow taper to the center and a slow taper to a sharp point. The leaf top is darker green than the bottom and begin to take on a yellow tinge as the leaf ages. Both sides have a sandpaper texture.

yellow ironweed leaf

Stem: A single stem grows up to 8 feet tall. The only branches are at the top leading to flowers. The green, ridged stem is winged with white hairs between the ridges and wings.

yellow ironweed under leaf

Root: The perennial roots are fibrous and have stout rhizomes so the plant forms colonies.

yellow ironweed stem

Fruit: The seeds develop inside a cage formed by the remains of the tube flowers. This opens to release the flat, brown seeds with small wings along their sides.

yellow ironweed fruit

Habitat: This plant prefers sunny places but will grow in light shade. It likes good soil with moisture as in lower pastures, along roadside ditches, along streams and bases of bluffs.

 

Yellow Ironweed

yellow ironweed plant

Yellow Ironweed has thick, stiff stems letting it tower over most other plants growing nearby. The stems are tough enough to withstand wind and remain upright. This lets it grow wherever it finds the right soil and moisture level.

The tall stems are popular with various vines. False buckwheat, partridge pea, hog peanut, woodbine, morning glories and more twine themselves around the stems and bind several plants together.

Recognizing this plant is fairly easy not only because of its size but by its flowers. The color is vibrant yellow. The back swept rays are irregular in number and arrangement. The globular crown of long, yellow disk flowers sticking out is totally different from the other aster family members. In those the disk or tube flowers are packed close together. Yellow Ironweed tube flowers are separate individuals.

This plant is determined to bloom and produce seeds. Even when the top is eaten off, the lower leaves send out new flower stalks. These will bloom on plants now only two feet tall. The leaves and stem tips do seem popular with deer.

The leaves are large and feel rough. As the plant blooms into the fall, the leaves take on a yellowish green color. The lowest ones turn yellow and drop off.

Yellow Ironweed forms colonies and seeds itself prolifically. These form yellow clouds of flowers along the roads and in the pastures from late summer into fall until frost kills the plants.

Wood Sage Teucrium canadense

In May single, thick, square stems appear pushing their way through the dense crowd of plants. In June conical spires of flowers top the stems and the first ring of pale lavender, almost pinkish, flowers open. The Wood Sage is in bloom.

Teucrium canadense L.

June – September                             N                                             Family: Lamiaceae

wood sage flower

Flower: A flower spike surrounds the top of the stem in whorls of two to six flowers. Green calyxes surround the bases of the flowers. Each flower has a large, white to pale lavender lower lip with dark purple mottling near the throat of the flower. Two short upright petals flank the lower lip like ears. The four stamens and pistil arch up over the lower lip. The edges and undersides of the petals are covered with short hairs.

wood sage side flower

Leaf: Opposite leaves have short or no petioles. Two leaf lie bracts spread out at the base of each leaf. The leaf is long and widest toward the middle and tapers to a point. The edges are toothed. Short hairs cover the top and bottom surfaces of the leaves. The mid and side veins form strong cords on the underside of the leaf.

wood sage leaf

Stem: Stiff square stems grow three to four feet tall. Fine short hairs cover the stems. Rarely the stem branches in the upper half.

wood sage underr leafRoot: The roots are fibrous and perennial. There are rhizomes so the plant forms colonies.

wood sage stemFruit:

Habitat: This plant prefers open, sunny areas with moist soils such as along creeks, roadside ditches and prairies.

Wood Sage

American Germander

wood sage plant

Wood Sage can be considered a weed. A single stalk appears one year. The next year the one stalk has become a small colony. Other single stalks appear nearby. In a few years Wood Sage covers the area.

Various smaller native bees don’t mind this abundance of food. They zero in on the purple splotches on the lower lip of the flowers and land to feed. For people, the flowers have no scent.

The flower spikes can be eight inches long. The tall stems bring the flowers up to where they are easily noticed. The flowers are small at three quarters of an inch long but are interesting to look at with their little ears.

Wood Sage is occasionally planted in native gardens. As with other mints, this one must be confined or it will take over the garden. It is a hardy plant tolerating some drought and crowding by other plants.

I find Wood Sage along the roads where it thrives even when surrounded by giant ragweed, blackberries and poison ivy. It does like lots of sun and withstands hot temperatures. The flower spikes make it an easy plant to identify.

Enjoy more nature essays about the plants, animals and events of an Ozark year in Exploring the Ozark Hills.

Physics 13 Using Rollers

Remember a simple machine doesn’t change the amount of work you do. You will still move an object the same distance. What a simple machine does is make that work take less effort. Are rollers a simple machine? What are rollers anyway?

These are not the kind girls use to curl their hair.

roller project materials

Question: How do rollers work?

Materials:

Book

String (scissors to cut it)

Rubber band

Six or seven round pencils

Procedure:

Wrap the string one and a half times around the book

measuring the string

I used a smaller book. The book could be twice as thick and this project will still work.

Cut off the piece of string

Tie a loop in one end of the string

loop in string

The loop can be an inch or a little more long. If it is less than half an inch, it will be harder to attach it to the rubber band.

Put the other end of the string through the rubber band and the loop

attaching the rubber band

The end of the string goes through the rubber band first and then the string loop.

Pull the string tight

loop around rubber band

The string loop must be pulled tightly to the rubber band so it will not slip pulling the book later.

Tie the string around the book

string around book

The string should be tied around the middle of the book so it will pull evenly across the table.

Use the rubber band to pull the book across the table

Set the book back at the beginning

spacing the rollers

The pencils should be fairly evenly placed so the book can move from one to the next without falling off.

Space out the pencils so three will be under the book and the others in front of it

Set the book on the last three pencils

Use the rubber band to pull the book across the pencils

Observations:

Describe how the rubber band behaves as you pull the book on the table

Pulling the book without rollers

Pulling the book across the table creates friction for the entire surface. Friction makes the book harder to pull.

Describe how it feels pulling the book on the table

Describe how the rubber band behaves as you pull the book across the pencils

Describe how it feels pulling the book across the pencils

Conclusions:

Assuming you pulled the book the same distance both times, did you do the same amount of work? Why do you think so?

Was it easier to pull the book on the table or on the pencils?

rollers under book

The pencils roll as the book is pulled over them making the name rollers apt.

What did the pencils do under the book as it went over the top of them?

Why would the pencils be called rollers?

Can you think of another name for a roller? What is it?

What I Found Out:

My book had a slick book cover on it so it pulled across the table easily. The rubber band stretches out at first then sprang back once the book started moving. The book dragged a little on the table.

The rubber band barely stretched before the book started pulling over the pencils. It moved very fast over the pencils. The book didn’t drag at all.

used roller pencils change spacing

The pencils do roll but some roll better than others. They are not attached to the book so they bunch up losing their spacing.

Since work is the distance times the mass, I did the same amount of work. The mass of the book and the distance did not change with and without the pencils.

What did change is how easy it was to pull the book over the pencils. The pencils turned and rolled under the book.

The pencils could be called rollers because that is what they did: rolled. Something else that rolls is a wheel.

Butterfly Weed Asclepias tuberosa

Butterfly weed, Asclepias tuberosa, is fast becoming a popular garden flower. It is one of the most easily seen and recognized of Ozark wildflowers.

My goal with these plant pages is to present information on a plant plainly. This post is set up for easy viewing online but includes the information and pictures used on the actual pages about butterfly weed.

I would appreciate any feedback you may have on this information either through the comments section or the Contact Page [this may be more reliable].

Asclepias tuberosa L.

May to September                                       N                                 Family: Asclepiaceae

butterfly weed flowers

Flower: Flowers range from lemon yellow through most commonly orange to red. The corolla is backswept. The five wells have the outer wall elongated and standing upright. The five horns arch over to the central disk. The flowers are in flat topped umbels from the tips of branches and nearby leaf nodes.

butterfly weed flower umbel

Leaf: The leaves are alternate and sessile. The top surface is dark green. The under surface is light green with a prominent midvein. The other veins are in a network. Short hairs cover the leaves especially the edges and veins.

butterfly weed leaves

Stem: The stem is hairy and ranges from green to purple. It goes up then bends over often with a branch or two.

butterfly weed stem

Root: This plant has a rhizome.

butterfly weed seed pods

Fruit: Each umbel can produce several long seed pods. They tend to stay slender with a groove down one side. They are covered with short hairs and ripen to a purplish brown. The groove splits releasing the tufted seeds into the wind.

butterfly weed seeds

Habitat: Butterfly Weed loves the sun. It grows along roadsides, in pastures, glades, open ground. It is often in drier areas.

Butterfly Weed

Chigger Flower, Pleurisy Root

butterfly weed plant

Asclepias tuberosa is a perennial so the plants show up in much the same places every year. Their flower color is so distinctive I watch for it trying to spot the first one to bloom.

Most butterfly weed around here is vivid orange. Some are paler, more yellow or even true lemon yellow. Some are deep red.

Some special flowers are two toned. They open as yellow. The backswept corolla remains so but the wells darken to red. These flowers are quite striking.

The greatest enemy of these plants is the roadside brush cutter. Unlike other milkweeds, butterfly weed will try to grow new stems and bloom again. It takes its toll on the plants and these may disappear after a few years.

Some of the older people in the area have successfully transplanted a special plant to their home. The fleshy fragile rhizome makes this very difficult. Failures are more common than successes but not mentioned.

The easiest way to have these plants in the home garden is to start them from seed or purchase nursery plants. I was told the plant can be propagated by layering as well. The low growth habit, prolific blooming, vivid colors and attraction of butterflies have made this a popular garden plant.

Although larger butterflies will stop by, I’ve seen pipevine and tiger swallowtails, most of the butterflies are smaller. Pearl crescent, little sulfurs, various skippers and gray hairstreaks hang around them creating a multicolored cloud. The usual wasps and bumblebees tromp around pollinating the flowers.

This milkweed is unusual in two ways. It has alternate leaves. It has clear instead of milky sap. Monarchs do lay eggs on it. Their caterpillars do seem to mature on the plants.

Whether growing wild or in a garden, butterfly weed is worth stopping and admiring.

Physics 12 Double Levers

Scissors are so useful. They are one of several common double levers.

Take a look at a pair of scissors. Each blade moves like a lever: one end goes down pushing the other end up.

Where is the fulcrum on a pair of scissors? Remember the lever turns on the fulcrum which remains in place. On double levers the fulcrum is where the two levers cross each other and are fastened together.

double levers scissors

I forgot to take a picture of my scissors. You know what they look like, don’t you? These are double levers. Do you see where the fulcrum is?

Get a piece of cardboard and a pair of scissors. Where should you put the cardboard to cut it the easiest? Close to the fulcrum or far away?

 

Let’s review how a fulcrum increases force. Get a 200 page book and 2 pencils. Prop the book on the end of one pencil. Put the second pencil crosswise under the first pencil to act as a fulcrum. Try lifting the book with the second pencil away from the book and near the book. Which placement makes lifting the book the easiest?

 

Should the cardboard be near the fulcrum of the scissors or farther away? Double check by trying to snip the cardboard from both positions.

double levers pliers

Pliers are a useful tool around the house. They can be used for gripping things or turning tight small lids. Do you see the two levers?

Another of the common double levers is a pair of pliers. Perhaps you have one to look at. Where is the fulcrum? Why are the handles for your hand to grip longer than the gripping ends of the levers?

double levers tin snips

Tin snips are used to cut sheet metal, flat plates of metal. The length of the handles can vary. As the handles get longer, will the snips part get more powerful?

On the farm I have another of the double levers. It’s called tin snips. These are used to cut sheets of metal such as metal roofing. If you don’t know anyone with a pair of these, you can look at the picture. Find the fulcrum. Like the pliers, one end of the levers is longer than the other.

 

Perhaps you can find some other double levers around your house. How do you recognize them?

 

What I Found Out:

The book lifted the easiest when the fulcrum pencil was close to the book. In the same way, putting the cardboard close to the fulcrum made cutting it much easier.

On both the pliers and the tin snips like with the scissors the fulcrum is where the two levers cross and has the bolt connecting the two.

Double levers are easy to recognize because they have two long pieces crossing each other and joined where they cross. That join is the fulcrum. Others I found included pruners for trimming plants, loppers for cutting brush and bolt cutters for cutting thick wires up to 1/2 inch thick.

Physics 11 Mass a Coin With Levers

Last Project we found out we could balance a heavy object with a light one by moving a lever over the fulcrum. Can we do this to mass a coin?

materials for project 11

Question: Can a lever be used to mass a coin?

Materials:

Piece of thin cardboard 3 cm x 28 cm

Dime

Balance

Metric ruler

Table

Procedure:

Mark a line 2 cm from one edge of the cardboard piece

Label the line R

marking the R line

The real purpose of the R line is to mark one end of the lever to tell the ends apart. It marks a good place to set the coin.

Place the cardboard piece on the edge of the table

Slide the piece over the edge of the table until it balances on the edge

balance the lever to mass a coin

As the cardboard lever moves out over the edge of the table, the end begins to rise. Take care it does not rise too far or the lever will slip to the floor.

Mark this point and draw a line across it

Label the line E

Measure the distance from line R to line E to the nearest mm

Mass the cardboard piece

massing the lever

Remember that a lever balances when the mass is equal on each side of the fulcrum.

Set the cardboard piece on the edge of the table

Set the dime centered on the line labeled R

Slide the cardboard piece over the edge until it balances on the edge

Mark this point and draw a line across it

Label this line 1

Measure the distance from the R side of the cardboard to line 1 in to the nearest mm

Mass the dime

Observations:

Mass of:

Cardboard:

Dime:

Distance:

R to E line:

Line 1:

Analysis:

Divide the line R distance by the line 1 distance for a mechanical advantage for the dime

Line 1 is used to mass a coin

Line 1 is where the lever balances with a dime on the R line. Go a millimeter too far and the dime slides down flipping the lever onto the floor.

Multiply this mechanical advantage by the mass of the cardboard to get a mass for the dime

Conclusions:

How important is balancing the cardboard to mass a coin?

How important is it to measure accurately?

Compare your calculated dime mass to your scale obtained mass.

Where is the fulcrum for your lever in this Project?

A lever has two arms. What were the two arms for the lever in this Project?

Do you think a lever is a good way to mass a coin? why do you think this?

 

What I Found Out:

Balancing a piece of cardboard on the edge of a table is harder than it sounds. I slid the cardboard piece out until it seemed balanced. When I moved toward my camera, it slid onto the floor. I started over again.

Since the distances are being measured to the millimeter and one of these is small, It’s important to get as close to the final balancing point as possible. Any breeze makes this impossible.

I used a regular ruler with centimeters and millimeters on one side and inches on the other. It helps that the 0 line for the centimeters is not on the edge of the ruler. This makes it easier to get an accurate starting place. If the 0 line was the edge of the ruler, I would have started on the 1 cm line and deducted the 1 from the reading. one reading did come out between two millimeter lines. I used the closest line for the distance.

careful balancing helps mass a coin

It takes care to keep the lever perpendicular to the table edge. You have to tap it lightly in the center, not on a corner to move it slightly until it balances.

I again had the lever slide to the floor with the dime on it. When I balanced the lever, the line R distance was 9.5 cm and the line 1 distance was 18.5 cm. The mechanical advantage was 0.51. Multiplying this by 3.5 g gave a coin mass of 1.9 g for the dime. My dime had a mass of 2.3 g on the scale. The two masses were close.

The edge of the table was the fulcrum. The R line marked one arm of the lever. The E line marked the other arm of the lever.

I don’t think this is a very good way to mass a coin. Finding the true balancing point is difficult. A regular ruler is not very accurate for measuring. There are too many places where errors can creep in.

Physics 10 Exploring Levers

The Greek Archimedes once said that given a fulcrum and a lever, he could move the world. Levers are another simple machine. What is it and how does it work?

materials for physics project on levers

Question: How do levers work?

Materials:

Wood slat 40 cm long by 5 cm wide

Triangular or 1” wood block [I found the 1” block works best.]

Several weights, 2 the same, 1 heavier, 1 lighter

Scale

Ruler

Pencil

Procedure:

Place the block on a table

Note: This is your fulcrum.

balancing the lever

The slat is not exactly level. This shows as my measurement of each end gave two slightly different values.

Place the wood slat on the block moving it back and forth until it balances

Note: The slat is your lever

Mark the balancing point

Measure from the end of the slat to the line from both ends

Mass your weights unless they are from a weight set so you know the masses

Keeping the balancing point over the fulcrum, place a mass at one end of the slat

unbalanced mass on lever

Placing a mass on one end causes that end to drop to the table while the other end rises.

Observe what the lever does

Place the identical weights, one at each end

Adjust the slat until it is again in balance

Take one weight off

Place the light weight on the other end of the slat

unbalanced lever

A teeter totter on a playground behaves this way when a heavier person sits down on one end. How can this person make it balance so both people have fun?

Move the slat back and forth until it balances

Measure the distance from the balance point over the fulcrum to each weight

Remove the weights

Return the slat to the original balancing line

Place the heaviest weight on one end of the slat and a lighter weight on the other end

Predict how you will need to move the slat to balance the two masses

Move the slat until the two are in balance

Observations:

Mass of weights

Distances:

From ends to balancing line

From masses to balancing line

Same mass weights

Mass and light mass

Mass and heavy mass

Describe what happens:

When you balance the slat

When one mass is put on one end of the slat

When the two identical weights are on the slat

When the light weight is put on one end

When the light weight is balanced

When the heavy weight is put on the slat

Prediction of where the slat will balance

When the heavy weight is balanced

Analysis:

Multiply the mass times the distance for the two identical masses

Multiply the mass and distance for the mass and the light mass

balancing levers

If you consider the formula of Fd = Fd it explains why a heavy mass is at a short distance to balance with a light mass.

Multiply the mass and distance for the mass and the heavy mass

Conclusions:

Compare the lengths when the salt is balanced.

If you could mass each end of the slat, how do you think these would compare?

Draw the lever, fulcrum and one mass

Put arrows to show where the forces are acting on the lever system

levers and vectors

The mass exerts mass downward on one end of the lever. That puts an equal upward force under the other end. The force vectors are equal and opposite so the center, on the fulcrum, has no net force acting on it.

Why does the slat balance at the same place when two equal masses are balanced?

How does the mass x distance results compare for the two identical masses?

How do these results compare for the light weight and the heavy weight?

A rule for levers is that the force times the distance for one arm or side equals the force times the distance for the other arm or side. Do you think this is correct? Why do you think this?

How can this be used to move a heavy object?

 

What I Found Out:

I tried using a triangular fulcrum. The slat would balance on the edge but it was very difficult to do this. It worked much better to use the 1” board piece as a fulcrum. I did have to watch that the slat was level as it would balance a little before it was really level.

balancing levers

I was in a hurry. I hope you take your time. My lever is not quite balanced between the 20 g and 50 g masses. You can tell because the slat is not level.

When I balanced the slat on its own, the ends measured 37.0 cm and 38.7 cm. This was nearly equal. The two ends would have the same mass as the slat would be divided in half.

The mass pushes down on the lever so it sinks to the table top. That means a force is pushing up the other end.

When I put masses of equal mass on the ends of the slat, the force pushing on each end was the same, the total mass of each end remained the same so it would balance at the same place as it did without the masses.

balancing levers

The balancing point puts equal mass on each side of the fulcrum. since the masses are equal, the rest of the set up is equal.

My two equal masses gave 740 g-cm and 772 g-cm. When I looked at the pictures of this, the slat wasn’t completely level so the two were probably even closer in size.

When I balanced the lighter mass, the slat moved the heavier mass closer to the fulcrum. The distances were 30.0 cm for the 50 g mass and 43.0 cm for the lighter20 g one. This gave the Fd values as 150 g-cm and 91.2 g-cm. The distances for the 500 g mass was 13.0 cm and 62.6 cm for the 50 g mass. The Fd values were 6500 g-cm and 3030 g-cm.

The Fd values for my experiment weren’t very close. This is the rule a lever normally follows so I need to look over my Procedure and Observations more closely.

The idea of a simple machine is to do the same amount of work using less effort. A lever would do this if the distance to the heavy object was short and the distance to where the force is applied is long. A long distance times a small effort will equal and larger effort over a short distance.

Physics 9 Simple Machine Called Wedge

Perhaps you have learned to sew on a button. Take a close look at the sewing needle. One end is a point. The needle gets thicker the farther up the needle you go. This is one kind of wedge.

needle is wedge

A yarn needle for sewing with yarn is large so it’s easy to see the pointed end and how the needle thickens going away from that end.

Find a door stop, one of the brown rubber kind that is pushed under a door to keep it open. Look at it from the side. It has a point and gets thicker farther from the point. this is another kind of wedge.

Maybe you know someone who carves wood. Ask to see a flat chisel. Look at it closely top and from the side. It starts at a broad point and gets thicker as you go away from the point. A chisel is a wedge.

wood chisel

Look at a wood chisel. Is it a wedge?

Question: How does a wedge work?

Materials:

Sewing needle

Piece of cloth

Procedure:

Look at the piece of cloth observing the thread pattern

Hold the piece of cloth

Push the needle through the cloth

Observe what the cloth does

Observations:

Describe and draw part of the piece of cloth

Describe how the cloth threads change as you push the needle through

wood chisel shows wedge characteristics

From the side it’s easy to see a wood chisel has a point at the end the slopes up from there.

Special Section on Wedges:

Look at the pictures of a splitting maul. Does it look like the other wedges? Why do you think so?

maul has wedge characteristics

A splitting maul has a typical wedge shape. The end comes to a broad point. The maul gets thicker going away from the point. Unlike the chisel this wedge goes out in two directions. The needle goes out evenly all around. All have a point.

Splitting mauls are used to split firewood. Usually the maul is swung down so the head hits the piece of wood. This is repeated as the crack in the wood widens until the piece splits into two pieces.

For this I used the maul as though it did not have a handle to show how the maul splits the wood. First I tapped the maul until it stood up in a piece of wood.

wedge point focuses force from the wedge

Even tapping the splitting maul enough so it will stand up creates a crack in the piece of wood.

Then I hit the top of the maul with a sledge hammer. This applies force to the top of the maul. Where does this force go?

The maul goes down into the piece of wood so some of the force pushes the maul downward.

The crack in the wood gets wider. Does some of the force go sideways? Why do you think so?

wedge puts force down and out

As the splitting maul goes further into the wood, the split gets wider. This crack follows the grain in the wood going to the center of the piece then splitting into two paths.

Conclusions:

When you push on a needle, you are applying force. Where does that force go?

How is a wedge like an inclined plane?

How is a wedge different from an inclined plane?

 

What I Found Out:

My piece of cloth had threads running up and down and other threads going across. The threads went over and under each other. They were tight so the threads did not shift.

When I pushed the needle through the cloth, the point went through between the threads and pushed them apart. After the needle went through the cloth, the threads tried to go back into place but left a small hole where the needle had been.

The splitting maul has a broad point and gets thicker going away from the point. It is a wedge.

The force goes into the maul. Part of the force goes down and pushes the maul further into the wood.

Part of the force pushes the wood apart. There must be force pushing the wood apart. The only place any force is being applied is on the top of the maul. Some of it pushed the wood apart.

An inclined plane has a broad point at one end and gets thicker going away from that point.

An inclined plane sits still. Objects are pushed or pulled up the ramp.

Force is applied to a wedge. That force pushed the wedge forward and pushes outwards to push things apart.

Physics 8 Exploring How Screws work

What do a pencil sharpener, a screw, a scissor jack and an inclined plane have in common? Find yourself several different kinds of screws and take a look.

types of screws

Common screws have one of two heads. The top one is a straight slot and takes a regular screwdriver. The bottom one has a cross slot and takes a Philips screwdriver.

Note: The raised metal going around a screw is called a thread. The top is called the head. Some screws have slots on their heads and take straight screwdrivers. Some have crossing slots and require a Philip’s screwdriver.

materials for project 8

Question: How do screws work?

Material:

Several different screws, same diameter but different threads

Screwdrivers for the screws

Block of wood with drilled holes the size of the screws in it

Ruler

Procedure:

Examine one of the screws closely to see how the threads are arranged

Hold a screw between your finger and thumb turning it with the other hand

turning screws by hand

The screw turns into the wood a tiny bit then the head cuts into my fingers as I try to turn it a little more and can’t make it budge.

Put the end of the screw in a hole in the board and try to turn the screw several turns using your fingers then use a screwdriver.

Take that screw out of the hole

Find two screws with different threads, one with threads far apart and one with threads close together

Start these two screws in the board until they stand up by themselves

wood furniture screw

The head is shaped like a wood screw’s head so this screw is used for wood. Fine threads are often used for fine work such as furniture.

Measure the height of the two screws

Turn each screw two complete revolutions

finely threaded screws

This was the longest screw as well as the one with the finest threads. If you measure from one thread down two, this should be the same as the amount turning the screw twice will put it into the wood. For this screw that was 0.2 cm.

Measure the height of the two screws

Observations:

How are the threads arranged on the screw?

How does it feel to turn a screw with your fingers?

How does it feel to turn a screw into the wood?

How it feels to turn a screw with a screwdriver

wood screw

This is a wood screw with definite threads not too far apart but not real close together either. The top will fit into the wood so it won’t catch on anything rubbed over the wood later.

Height of the screws:

Wide thread

beginning

ending

medium threaded screws

At first glance this screw went in the farthest but it was the shortest so it really only went in 0.4 cm in two full turns.

Narrow thread

beginning

ending

Conclusions:

If you could unwrap the threads on a screw, what simple machine would they become? Why do you think so?

Why do we use a screwdriver to put in a screw?

Compare how fast a screw with wide threads goes in to one with narrow threads.

comparing screws

Looking at the three screws it is easy to see the right one has fine threads and the left on has coarse threads. The middle one is in between the other two.

What I Found Out

I had three screws. One had coarse threads. One had fine threads. One was in between.

When I held a screw and turned it, it crawled up between my fingers. It felt like my fingers were sliding up the threads.

Of course I can’t really take the threads off. But if I could, the thread would become a slanted line and be like an inclined plane from the bottom to the top of the screw. I think that because the thread is a continuous line going up the shaft.

starting coarsely threaded screw

This is a deck screw. It has widely spaced threads to make it easy to put it into coarse wood. The top is angled to fit into the wood smoothly so the deck surface will be smooth.

Trying to put a screw into a hole in the wood using fingers does not work. The very tip will go in but then the fingers can’t turn it anymore. A screwdriver gives more power to my hand and makes the threads go into the wood.

coarsely threaded screws

After two full turns the coarsely threaded screw was only 1.5 cm high. It went in 0.6 cm.

My screw with fine threads started at 2.6 cm and ended at 2.3 cm so it went in .3 cm. The medium threads started at 1.7 cm and ended at 1.3 cm going in .4 cm. The coarse threads started at 2.1 cm and ended at 1.5 cm going in .6 cm.

Coarse threads go in much faster than fine threads.

Physics 7 Mechanical Advantage

The reason for using a simple or complex machine to do work is to use less effort or force to do the same amount of work. How much force a machine will save is its mechanical advantage.

materials for physics 7

Question: What is the mechanical advantage of an inclined plane?

Materials:

2 boards, one twice as long as the other

stack of thick books, at least four 5 cm or more thick

spring scales

Procedure:

Set up the stack of four books

Measure the height of two, three and four book stacks

Lift your block using the spring scale to the top of the stack

finding work being done

The blocks are being lifted to the top of the book pile. No matter how the blocks get there, this is the work being done. Lifting a heavy weight is easier using a ramp. Mechanical advantage determines how well the ramp works.

Record the force needed

Measure the length of the two boards

Set up one board as an inclined plane to the top of the stack of four books

Pull the block up the ramp recording the force needed

mechanical advantage is efficiency

Pulling a weight up a ramp takes less effort than lifting the weight straight up. How efficient is the ramp?

Remove one book from the stack

Pull the block up the ramp recording the force needed

Remove another book from the stack

Pull the block up the ramp recording the force needed

Replace the ramp with the other board

Pull the block up this ramp recording the force needed

Add a book to the pile

Pull the block up the ramp recording the force needed

Add the last book to the pile

Pull the block up the ramp recording the force needed

Analysis:

Calculate the work done lifting the block up the height of two, three and four books using the formula W = Fd.

mechanical advantage of a short ramp

The short ramp is much steeper and takes more effort. It is also shorter. Is it more efficient? Is its mechanical advantage greater?

Calculate the mechanical advantage of the inclined planes using the formula M.A. = R/E where R is the force needed to lift the block up the pile of books and E is the effort or force needed to pull the block up the ramp.

Another way to calculate the M.A. of an inclined plane is to divide the length of the plane by the height it goes to. Use these measurements to calculate the M.A. of your ramps.

Conclusions:

The scale reading when you lifted the block up is the mass of the block, the force needed to lift it and the resistance for calculating mechanical advantage. How can it be all three?

How do the M.A. you calculated using R/E and using L/H compare? Should they be the same? If yours are not, why not?

mechanical advantage decreases with height

The shorter the height and/or the longer the ramp, the less effort is needed to get the blocks up onto the books. Do these increase mechanical advantage of the ramp?

Does a short or a long inclined plane have more mechanical advantage?

Does the height of the ramp end matter for the mechanical advantage?

The total amount of work done by each ramp for each pile of books was the same. What was not the same?

mechanical advantage is ramp length divided by height it goes to

The work done is the same so, why use a ramp? How do you get the most mechanical advantage out of a ramp?

What I Found Out:

My scale read 200 g lifting the block up the pile of books.  Two books were 14.5 cm high making the work done 2900 g-cm. Three books were 21.5 cm tall making the work done 4300 g-cm. The tallest pile of four books was 29 cm high making the work done 5800 g-cm.

The mass of the block is the pull of gravity on it. Lifting the block requires enough force to counter gravity, equal to the mass. Since gravity is pulling on the block, it is resisting being moved by the mass amount making the force needed to lift the block equal to the resistance from gravity which is the mass of the block.

The two boards I used were 74 cm and 105 cm long.

My long board was 1.5 cm thick so I added that to the height of the stacks. The short board was .5 cm thick.

For the short ramp the force needed was 100 g [2 books], 130 g [3 books] and 150 g [4 books]. For the long ramp the force needed was 80 g [2 books], 110 g  [3 books] and 130 g [4 books].

Using the first formula the mechanical advantage for the long ramp was 2.5 [2 books], 1.8 [3 books] and 1.5 [4 books]. For the short ramp the mechanical advantage was 2 [2 books], 1.5 [3 books] and 1.3 [4 books].

Using the second formula the mechanical advantage for the long ramp was 6.6 [2 books], 4.6 [3 books] and 3.4 [4 books]. For the short ramp the values were 4.9 [2 books], 3.7 [3 books] and 2.5 [4 books].

My calculated mechanical advantages by the different formulas were very different. I had expected them to be similar. Perhaps my measurements were not as accurate as they should have been.

The special formula for calculating mechanical advantage for an inclined plane is the second one so I would prefer using those values. Another reason I would favor those is that my spring scales are not easy to read and inaccurate whereas my meter stick and rulers are easy to read and much more accurate.

Both ways indicate the longer ramp has a greater mechanical advantage. This value went down as the height the ramp went to became greater.

In all cases, the height of the book pile was the same for the 2, 3 and 4 books. The amount of work done was the same. What really changed was the distance the blocks had to be moved to get to the top of the book piles.

Physics 6 Meet the Inclined Plane

You are going to visit a friend and run up to the porch. How are you going to get onto the porch? You can jump up or you can walk up the steps.

Jumping up may be more fun. Walking up takes less effort. Those stairs are one kind of inclined plane.

Hailyann workman pulling blocks up ramp

Hailyann Workman’s help was greatly appreciated on this project. She seemed to think this was fun to do.

Question: How does an inclined plane work?

Materials:

3 Boards or pieces of stiff cardboard 10 cm wide and 0.5 m, 1 m and 1.5 m long

3 Bricks or 3 books about 5 cm thick

Spring scales

Meter stick

Block with loop

Procedure:

Set up the pile of books

Measure the height of the pile of books

Stand the block next to the pile of books

Use a spring scale to lift the block onto the books recording the force in grams

Remove the block

Measure the length of the boards

short inclined plane

A short ramp is steep. Since work is force times distance, the longer distance makes the amount of work much higher.

Lean the short board on the pile of books to form an inclined plane or ramp

Set the block just on the edge of the board

Use the spring scale to pull the block up onto the books recording the force needed

Repeat this for each of the other boards

Observations:

Height of book pile:

Length of short board:

Length of medium board:

Length of long board:

Force needed:

To lift the block

Short board

Medium board

Long board

Analysis:

Calculate the work needed to get the blocks onto the books by multiplying the force on the scale times the height of the books. This is W = Fd or Work = Force times distance.

Using a simple machine is supposed to reduce the force needed to get the same amount of work done. Now that we know how much total work is needed, we can calculate the force needed for each of the inclined planes by rearranging the formula so W/d = F or work divided by distance equals force.

Calculate the force needed for each inclined plane.

Go back to the Procedure to complete the Project

Conclusions:

Compare the force you measured for each inclined plane with the force you calculated.

Compare the force needed for each ramp with the force needed for the others and to the force needed to lift the blocks.

medium length inclined plane

A longer ramp has less of a slope making it easier to pull the blocks up.

What happens to the distance you must pull the block to use less force?

Would it be better to lift or use a ramp for a lightweight object? Why do you think so?

Would it be better to lift or use a ramp for a heavyweight object? Why do you think so?

What is the advantage of using a ramp?

 

What I Found Out:

This week I found Hailyann Workman to help me do this project. She is five and in kindergarten. She thought pulling the blocks up a ramp fun to do.

My stack of books was 15 cm tall. The scale registered 200 g lifting the blocks up. The work done was 3000 g-cm.

The short ramp was 44.5 cm long. The scale showed 150 g needed to pull the blocks up the ramp. I calculated 67.4 g-cm.

Next the blocks went up a 74 cm ramp using 100 g of force. I calculated needing 40.5 g-cm.

long inclined plane

Remember finding out about friction last week? My long ramp was rough making lots of friction. Covering the ramp with paper made it smooth.

The long ramp was 109 cm and rough. It was hard to pull the blocks up so I taped paper onto the ramp to make it smooth. The blocks pulled up easily with 70 g of force needed. My calculated amount was 27.5 g-cm.

My measured forces were much higher than my calculated forces. Perhaps I misread the scale. My block was smooth but not slick. My ramps were not slick so there was friction.

The needed force did decrease as the ramp got longer. The medium ramp took half the force of lifting the blocks.

The distance increases as the force needed decreases.

A lightweight object can be lifted up to move it the shortest distance. A heavyweight object should be moved up a ramp. This takes more distance but requires less force and is easier on you than lifting something heavy.

A ramp is a way to decrease the force needed to move an object even though it increases the distance needed to move it.

Physics 5 Exploring Friction

Rub your hands past each other once. What do you feel?

My hands feel rough against each other. I can feel friction between them.

Now rub your hands back and forth a dozen times or so. What happens?

My hands warm up. I use this when my hands get cold in the winter.

Friction makes the heat. It does other things too.

friction project materials

Question: How does friction work?

Materials:

Smooth block of wood like a couple of inches of a 2 x 4

2 Pieces of Sandpaper

Tape

Smooth board about 0.5 m long

Meter stick

Procedure:

Rub the block of wood on your hand

Describe how it feels

Rub the piece of sandpaper on your hand

Describe how it feels

Push the block of wood down the smooth board

Describe how it feels

Set the block of wood on one end of the board

Lift that end of the board until the block slides down the board

smoother surfaces have less friction

It didn’t take long for the block to slide down the varnished board. The two smooth surfaces had little friction between them.

Measure how high you lifted the board

Tape the sandpaper rough side out on the block

sandpaper on block

The sandpaper on the block felt very rough especially compared to the smooth sanded block surface.

Push the block on the board

Describe how it feels

Set the block on one end of the board

Lift that end of the board until the block slides down the board

Measure how high you lifted the board

Tape a piece of sandpaper on the long board

board covered with sandpaper

I had a long piece of sandpaper used on a belt sander so it covered the length of the board.

Push the block on the long board

Describe how it feels

How high do you think you will have to lift the board this time?

Set the block on one end of the board

Lift the end of the board until the block slides down the board

Measure how high you lifted the board

Observations:

Describe how the block feels against your hand

Describe how the sandpaper feels against your hand

Describe pushing the block on the board

Describe pushing the block with sandpaper on it down the board

Describe pushing the block with sandpaper down the board with sandpaper

How high do you think you will lift the board the last time?

Measurements:

Plain block on plain board

Block with sandpaper on plain board

Block with sandpaper on board with sandpaper

smooth surfaces still add to friction

Even the varnished board was rough enough for the sandpaper to hold to and keep the block from sliding down.

Conclusions:

Does the block or the sandpaper have more friction? Why do you think so?

Which of the three times you lifted the board was there the most friction? Why do you think this?

What did increasing the friction between the block and board do?

How could you decrease the friction between the block and board?

How could you increase the friction between the block and board?

Car tires use friction to keep and move the car on the road. What creates this friction?

Why is it important to not have smooth tires?

Why is driving on ice so dangerous?

friction keeps the block from moving

The block seemed stuck to the board as I raised the board higher and higher. Shortly after taking this picture, the block tumbled down the board.

What I Found Out:

My block was a piece of a two by four so it was sanded smooth and felt smooth against my hand. The board was varnished on one side and that side felt slick. Rubbing them against my hand made my hand a little warm.

I put the block on the varnished side of the board and lifted the end. The end was 17.3 cm high when the block slid down.

The sandpaper was rough on my hand and made my hand hot rubbing it. I put the block on the varnished side of the board and started lifting that end. It was 30.5 cm high before the block slid down.

When the block with sandpaper on it was set on the board with sandpaper on it, I had to lift the end up 35.5 cm and the block tumbled off instead of sliding.

The block had a lot less friction than the sandpaper because it felt smooth and only warmed my hand up rubbing it. The sandpaper scraped my hand and made it feel hot.

Friction makes it harder for an object to move so the third time with sandpaper on both the block and the board had the most friction. I had to raise the board really high to get the block to move and then it fell off.

The smooth block and board had  the least friction so any way to make them smoother would decrease the friction even more. Using rougher sandpaper on both the block and board would increase the friction.

A car tire has treads. Roads are usually rough. Rougher kinds of tread and rougher roads would increase the friction. Smooth tires would have a lot less friction letting the tires slide on the road.

Ice is really smooth and slick. It would reduce the friction a lot so the tires would slide.

 

Physics 4 Exploring Work in Physics

Picture yourself helping to push a car. You shove. You turn around and push with your back. The car doesn’t move. Did you do any work?

According to your muscles you did a lot. According to the physics definition you did none.

In physics work is defined as moving something over a distance. Since the car did not move, you did no work. In physics this is written as: W = FD or work equals force times distance.

work project supplies

Question: How much work do you do?

Materials:

Spring scales [My set of 3 has a sensitive scale, a medium scale and a harder scale.]

Several blocks of different masses

Note: Another solution is to have stackable blocks.

Ruler

Procedure:

Each block will need a small loop to hook the spring scale to. An easy way to make such a loop for lighter blocks is to take a length of masking tape, attach one end to the block, crimp a length of the tape and attach the other end beside or over the other end on the block.

tape loop on block

The masking tape loop will only work for pulling light objects. It does a good job for that and is easy to make.

Place a block on a smooth table top

Set the ruler so you can see how far you will move the block

Hook a spring scale to the block

pulling a block with the scale

It is important to pull steadily on the spring scale but reading the force can be difficult. Be sure to read it when the blocks are moving along.

Pull the block steadily for 30 cm

Observe the amount of force on the scale in grams

Note: If the scale barely moves, try a scale with a more sensitive scale on it.

Repeat this for each block or additional block

Observations:

Record the distance and force for each block

work requires going a distance

My wood scrap blocks were mostly flat pieces making them easy to stack for pulling.

Analysis:

Multiply the grams times the distance in centimeters for each block to get the work done for each block.

Conclusions:

Which block has the most mass? Why do you think so? [You can check this by massing the blocks.]

Do you do more work moving a block with less mass or more mass?

work requires force

Each block added to the stack increased the amount of force needed to pull the stack.

If you pulled a block 15 cm, would you do more or less work? Why do you think this?

 

What I Found Out:

I used some scrap wood pieces for blocks so they came in various sizes and shapes. The biggest one was the one I chose to put the loop on. the others were piled on top of it one by one to increase the mass pulled by the spring scale.

The first block took 6 g to pull it the 30 cm. This made the work done 180 g-cm.

Two blocks took 40 g to pull the same distance. Now the work done was 1200 g-cm.

Three blocks took 49 g to pull. Now the work done was 1470 g-cm.

Four blocks took 52 g of effort making the work done 1560 g-cm.

Five blocks took 75 g of force making the work done 2250 g-cm.

Six blocks took 85 g of force making the work done 2550 g-cm.

Seven blocks took 90 g of force making the work done 2700 g-cm.

work done pulling 7 blocks

The last block was added to the stack. The pile was pulled for the 30 cm so work was done.

The more blocks on the pile, the more force it took to pull the pile across the table. That makes me think a heavier block will take more force than a lighter one.

Looking at the increases in effort, the first block took 6 g but the second took an additional 34 g so the second block must have more mass than the first one.

The third block increased the force 9 g and the fourth a mere 3 g. These are lighter than the second block.

The fifth block increased the force needed 23 g. The sixth added 10 g and the last one 5 g. The second block was the biggest block with the fifth block next.

Pulling the first block 30 cm required work of 180 g-cm. If I had pulled the block only 15 cm, it would be 6 g times 15 cm or 90 g-cm. It takes less work to move half the distance.

Physics 3 Using Vectors To Show Forces

You are asked to join a game of tug of war by one friend. Each of you grabs an end of the rope and starts pulling. Neither of you can pull the other one.

Another friend comes over and grabs the rope with your friend. What happens?

At first the forces you and your friend exert on the rope are the same and opposite. The result is no force.

Let’s show this using vectors.

using vectors to show tug of war forces

A vector is an arrow pointing in the direction the force is going. In tug of war the forces go away from each other as both sides are pulling on the rope.

When the third person starts pulling, one force stays the same. The other force doubles. Can vectors show this?

using vectors to add forces

There is one vector arrow for each tug of war participant. Each arrow points the way that person is pulling. Two of the arrows are equal and opposite cancelling each other out. That leaves one arrow to show what happens in the game.

When you put the vectors together, they show what happened in your game of tug of war.

 

What Is a Vector?

As you can see, a vector is an arrow. The arrow shaft shows the amount of the force. You can do this with labels or drawing to scale.

The head of the arrow shows the direction the force is acting in.

 

Let’s Draw some Vectors

Materials:

Paper or Graph paper

Pencil

Ruler

Drawing the Vectors:

Draw your block from Project 1

From the bottom center of the block draw a line 2 cm long straight down

using vectors to show gravity

Every object on Earth has this vector arrow pointing down. If that force didn’t exist, everything would float into space.

Put the head of the arrow on the end going down

What does this arrow show? What force is holding the block on the table?

You made the block move by pushing on it. Draw a line to the side of the block. How long should the line be?

using vectors gives information about forces

Using vector arrows for forces makes it easy to see how strong a force is, which direction it is going and how it is acting on an object.

The block moved. Think back to the game of tug of war. As long as the two forces were the same, the forces cancelled each other out.

If the force line showing you pushing the block is shorter than the gravity arrow, will the block move?

Your push vector must be longer than your gravity vector. Let’s make it 3 cm long. Now put the head of the arrow on.

Where does this go? Which way did the force push? It pushed against the block so the head of the arrow points at the block.

Can you draw the pulling force on the block using vectors? Try it. My drawing will be down below.

 

Using Vectors for Changing Forces

Put your block out on the table. This time push on the block from two adjacent sides at the same time.

two forces pushing block

Gravity always pulls on objects on Earth. This time we are interested in two forces pushing on two adjacent sides of the block at the same time. Which way will the block move? Can vectors be used to tell us?

Which way did the block go?

Draw your block on the graph paper again. This time have two pushing forces on adjacent sides on the block.

Now, copy one of the vectors from the tip of the opposite corner. Make sure it points in the same direction and is the same length.

using vectors to show movement

The vector arrows are the same ones as before only moved. they point the same way and are the same length. Moving the vectors lets you draw a resultant vector showing the actual path the block took when acted on by two forces.

Next copy the other vector with the end starting at the point of the other vector. Make sure it points in the same direction and is the same length.

If you draw a final vector from the point of the block to the point of the last vector, you have the direction the block moved when you pushed on it with two forces.

using vectors to show pulling

The vector arrow for gravity still points down. The other vector arrow now points away from the block as you were pulling on it.

Why Use Vectors?

You can see the forces acting on your block, right? You can see some of them but not others.

Using vectors makes what is happening easier to see. As we go on to look at work and simple machines, we will often use vectors to better understand what the forces are doing.

Physics 2 Putting Forces Together

Do you like to fly paper airplanes? The beginner model doesn’t fly very well. A modified one zips along.

What do paper airplanes have to do with physics and forces? They can show us how putting forces together changes the strength of the forces.

Tyler Green

Introducing my helper for this physics project Tyler Green.

Question: How does putting forces together change them?

Materials:

Paper airplane

Fan

Tape

Large room

Procedure:

Make your favorite paper airplane

Set up the fan at one end of the large room

Stand by the fan, not turned on, and fly your paper airplane

throwing a paper airplane

Paper airplanes have several forces working on them. Air pushes them up and back. Your hand pushes them forward. Gravity pulls them down. Tyler isn’t thinking about this as he practices flying his airplane.

Put a piece of tape where it lands

Repeat this two more times

Turn on the fan

Fly your paper airplane several times over the fan so the moving air catches it

Mark where the airplane lands each time

Walk out from the fan to about where your paper airplane would land with the fan off

Fly your paper airplane toward the fan and into the stream of air several times

Mark where it lands each time

Observations:

Describe where the paper airplane lands

Without the fan

With the fan

Against the fan

Describe how the paper airplane flies

Without the fan

With the fan

Against the fan

Conclusions

What forces are acting on your paper airplane when it flies without the fan?

Does the air from the fan provide a force?

putting forces together can mean increasing the forces working on an object

Who says physics is boring? Not Tyler. His paper airplane really took off when the fan’s air current helped push it aloft and across the room.

What happens when this force is added to your paper airplane?

What happens when this force acts against your paper airplane?

How does putting forces together change the force acting on an object?

 

What I Found Out:

It is hard to fly a paper airplane and take pictures of it flying at the same time. I asked Tyler Reed for help. He was a bit young for the physics but very enthusiastic about flying the airplanes.

A paper airplane launched into the air has several forces acting on it. One is the push you give it to make it go called thrust. Another is gravity pulling it down to the ground. Another is the air which helps hold it up but pushes against it slowing it down.

Tyler had a lot of thrust so the paper airplanes, two styles, flew very well without the fan. They zipped along moving up a little then going lower until they hit the floor at the laundromat where I do the physics projects as there is so much more room than at home.

With the fan turned on the paper airplanes flew higher and farther before. This depended on Tyler throwing the planes near the fan so the fan’s air could push on them.

adding forces together can slow objects down

Tyler threw the paper airplane at the fan. If you look carefully you can see the airplane off to the right side and slightly below the fan pushed there by the air current.

Then Tyler threw the paper airplanes at the fan. The air was still being pushed out from the fan. Now the air stream was pushing against the airplanes. They tended to go up over the air current, turn aside out of the current or dive bomb into the floor.

Putting forces together changes how an object moves. When the forces act in the same direction, they add up to a bigger force so the object moves farther. When the forces act against each other, they make the object go slowly, stop or turn aside from the force.

OS10 Water Balloon Pressure

 

Water shot out of a hole in a can in an arc to the ground. The greater the water pressure behind the hole, the longer the arc. As the pressure fell, the arc shrank. Shouldn’t a hole in a water balloon act the same way?

filling the water balloon

Question: What happens to water coming out of a hole in a water balloon?

Materials:

Balloon

Pin

Water faucet in a large sink or hose

Block to set the water balloon on

Procedure:

Blow the balloon up about half way

Hold the neck closed and push on the balloon

How does the air behave?

hole in water balloon

It is easier to put a single hole in a partially blown up balloon. If the balloon is blown up too much, it will break.

Make a pin hole about half way down the balloon

Let the air go out of the hole

How does the balloon change as the air goes out?

Slide the neck of the balloon over the end of the faucet or hose [wetting it first makes this easier]

water balloon on faudet

Even if the mouth of the balloon is tight on the faucet, hold it on as you put water in the balloon.

Place the block so the balloon will sit on it as it fills up

Turn the water on slowly to fill the balloon

How does the water come out through the hole?

What happens to the hole?

Turn the water off when the balloon is about two thirds full

Observe how the water and the balloon act as the water goes out of the water balloon

Warning: Do NOT take the balloon off the faucet until almost all of the water is out of it‼!

Observations:

How does air behave

When you push on an air filled balloon

When the air comes out of a hole in the balloon

Describe how water acts as you fill the water balloon

water balloon filling

Like the water from the hole in the can, water arcs out of the hole in the balloon

Describe what happens to the hole

Describe what happens as the water balloon empties

Describe what happens to the balloon as it fills and empties

Conclusions:

Why does putting pressure on one part of an air filled balloon make another part bulge?

What happens to the balloon as you put pressure inside of it?

Why does the water arc get thicker as more water goes into the balloon?

water balloon with long water arc

The balloon stretches out and has elastic energy adding pressure to the water in the balloon making the water arc much bigger than the one from the can.

Compare the water arcs from the cans to the one from the balloon.

Why does the water arc from the balloon last so long?

 

What I Found Out:

I had some big round balloons. It was easy to blow one up just a little and poke a pin hole in it.

The balloon fit on the faucet in my bathroom sink tightly. I turned the water on a little.

For a few seconds water dripped out of the hole and ran down the balloon. After that the water arced out of the balloon. The balloon got bigger and so did the arc. Then both stopped changing.

I turned the water on a little harder. The balloon got a little bigger. The arc had more water in it but didn’t seem any bigger.

A balloon stretches as it gets bigger. A letter written on a balloon gets bigger as a balloon gets bigger. The hole got bigger so more water could get out.

I turned the water on a little more. The balloon got bigger slowly. The arc straightened out and had more water in it.

water balloon emptying

Taking the mouth of the balloon off the faucet before the balloon is empty lets the water form a geyser out of the mouth. This is only fun if you are outside on a hot day.

My sink was far too small. When the balloon got about eight inches across, the arc shot out over the sink and onto the floor.

When the water ran out of the can, the arc quickly shrank. The arc of water out of the balloon stayed up for a long time.

When I was done, I took the balloon off the faucet. Water shot up out of the mouth of the balloon like a geyser.

Only air and gravity put pressure on the water arcing out of the can. The balloon put pressure on the water inside of it making the arc large for a longer time and shooting the water out of the mouth when I took it off the faucet.

Physics 28 Building Arches

Lots of bridges have arches under them. The Romans used arches under their aqueducts for thousands of miles carrying water to their cities. What’s so special about arches?
materials for project 28
Question: How does an arch work?
Materials:
Paper
Tape
Procedure:
Make two small diameter paper tubes

paper tubes

The two tubes should be a small diameter and about the same diameter.

Overlap the ends 2 cm and tape them together [You will need to flatten the ends.]

overlapping the 2 paper tubes

The two tubes only need 2 or 3 cm overlap but must be flattened for the overlapping part.

Bend this long tube into an arch but don’t fold it

taping the joint

The tape must extend over the paper joint on both sides.

Place one end of the arch against a book or other heavy thing
Hold the other end lightly to make it an arch
Press down on the center of the arch letting the end move if it wants to
Hold the end of the arch firmly in place
Press down on the center of the arch
If you can, suspend a cup from the center of the arch and fill it with weights
Observations:
Describe what happens to the end of the arch when you put pressure on the top:

arches divert forces down their legs

Force applied to the top of an arch flows down each leg into the ground or other base under the arch.

Describe what happens when you hold the ends firmly and put pressure on the arch:
Conclusions:
Where does the pressure go when you press on the arch?
How does this make the arch a good way to build a bridge?
What must a builder do to use an arch safely?

arches tend to spread under force

When weight or force is applied to an arch, the base of the arch tends to spread. This tendency must be countered when the arch is used in construction.

If two arches are side by side, what happens to the forces acting on the bottom of one arch?

What I Found Out:
My arch tried to fold at the sides of the flattened part a little making the top look a little flat. When I pressed on the center of the arch the first time, the free end moved out letting the arch flatten.
The pressure I put on the arch went down both legs of the arch. The one leg was trapped against the box and wall so the force pushing that leg out was stopped by force from the wall. The free end had no force acting against it so the end moved outward.

paper arch

Arches are more rounded than this paper version but this one shows how arches move forces so they can support a lot of weight.

When I held the second leg firmly in place, I supplied the force against the outward force. The arch held firmly.
I could not suspend weight from my arch but think the cup would hold a lot of weight. The force from the weight would go down the legs into the table and the wall and my hand.
Since an arch moves the force from weight off the bridge, the bridge can carry a lot of weight. Since the arch has an opening in the middle under it, other traffic or water can move freely below the bridge.
The problem with using an arch is the outward force acting on the legs. There has to be something strong pushing back to keep the arch in place.
Two arches side by side will do this for each other. The outward force from one leg pushes against the leg from the next arch which is pushing back as weight force moves onto it.

Physics 27 Making Walls Stronger

Changing the shape of a sheet of paper made it much stronger. But people don’t live or walk on tubes or folds. People live in buildings with walls.

The sheet of paper got stronger when forces were moved from the center to the edges of the paper. Can walls do the same thing?

materials for physics 27 project

Question: How can walls be made stronger?

Materials:

Paper

Tape

Ruler

Scissors

Procedure:

nine tubes completed

The physics project will use nine tubes of about the same diameter.

Make 9 small diameter long tubes of paper

tubes to make square completed

The four tubes for the square must be shorter than the two used for the diagonal pieces. The distance diagonally across the square is farther than across a side.

Trim 6 cm off the ends of four tubes

arranging the tubes for the square

I put each left tube on top of the right tube so the square would be close to a square not a rectangle. You can do the opposite as long as you do the same for each corner.

Tape the four trimmed tubes into a square

taping the corners together

A strip of tape across each corner on both sides held the tubes in place. The tape wrapped around the tube at each end about half way.

Hold the square in one hand or with the bottom on a table

completed tube square

The tape crossing each corner holds the square together. Is the tape strong enough to hold the square together?

Push the side

pushing on the side of the square

Pushing on one side of the square makes the side slope. All the pushing force goes across the top tube to push on the top far corner making it buckle.

Tape a tube diagonally across the square

taping the diagonal tube in place

The diagonal tube is taped into place. Notice the tape itself stiffens the corners.

Hold the square in one hand or with the edge on a table

square is stronger with a diagonal in it

Putting a diagonal inside the square wall cut it into two triangles. Pushing on one side with another side of the triangle on the table is like pushing on the triangle. The side does not move.

Push gently on one side then the other side of the square

Tape a tube diagonally across the square in the other direction

two diagonals in the square make it much stronger

Both diagonals must be flattened a little in the center so the two diagonals will lie flat.

Hold the square as before

Push gently on one side then the other side of the square

making the triangle

Laying the tubes out for the triangle shows that each corner has less angle than those of the square.

Tape three tubes into a triangle

taping the top of the triangle

The tubes meet at an angle so I flattened the tips a little and taped over the top of the joint.

Hold the base of the triangle in one hand or on the table

Push on one side then the other side of the triangle

Observations:

Describe how the square feels to hold

Describe what happens when you push on the sides

Describe how the square with one diagonal feels

one diagonal makes a wall stronger but not strong enough

Pushing on the side of the square with one diagonal going up makes the square twist. The pushing force tries to push on the far corner but the diagonal tries to take the force back to the table not letting the corner move.

Describe what happens when you push on the sides

Describe how the square with two diagonal feels

Describe what happens when you push on the sides

Describe what the triangle feels like when you hold it

Describe what happens when you push on the sides of the triangle

Conclusions:

Is a plain square very stable? Why do you think so?

Why did you have to trim the four tubes for the square?

What has the square become when you add a diagonal?

pushing on triangle side

The triangle side does not push over. The force goes down the other side and into the table.

Compare how the square with a diagonal and the triangle act when pushed on.

Compare how the square with two diagonals and the plain square feel when you hold them.

Compare how the force of a push on the plain square compares to the force of a push on the square with one or two diagonals.

Why do you think the diagonals make a wall stronger?

Can you think of another way to make a square wall stronger with out using diagonals?

Try your idea out and see if it works. Compare your method to the diagonal method.

 

What I Found Out:

The plain square was very flimsy. It was easy to push the side over turning the square into a rhombus. This is not very stable.

The longer tube fit into the square. If the sides had not been trimmed, the longer tube would not have been long enough to reach across the diagonal.

Once the diagonal is in place the square becomes two joined triangles. It feels much stiffer than the plain square did. The sides do not push. The square does twist when I push on the side.

The sides of the triangle did not move when I pushed on them. The triangle felt rigid.

The square became two triangles with the diagonal in place so the sides did not want to move. But pushing on the top triangle made the side twist because it was not flat on the table.

pushing does not move the square with two diagonals

Pushing on the side of the square with two diagonals in it has the forces being split so some goes across the top, some from the top to the bottom down the diagonal even some into the second diagonal. The square will not push.

With two diagonals in it, the square is stiff. It feels rigid, not at all flimsy like the plain square. The sides do not move when pushed. It does not twist.

When I pushed on the side of the plain square, all the force went across the top tube to push on the other side tube. It moved.

When I pushed on the side of the square when the diagonals were in place, some force still went across the top. But some of the force went down the diagonal to the base of the square.

Diagonals make the square stronger by redirecting the force, breaking it up. That way less force pushes on the top of the side tube and it doesn’t move easily.

The square gets stronger if the corners do not move. Diagonals move the forces around. If the corners are reinforced somehow, it would take a lot more force to move them.

One way would be to put small diagonals across each corner. Another way would be to put a solid piece over the entire square to hole the tubes in place.

Physics 26 How Strong Is a Paper Bridge?

We met force as a push or a pull. When we balanced forces, we found we could set two forces against each other. The new force was found by adding those forces up.

When an engineer builds a building or a bridge, forces are very important or the structure will fall down. How can an engineer move forces around to keep a structure standing?

materials for project

Question: How strong is a sheet of paper bridge?

Materials:

Several sheets of paper

Tape

Plastic yoghurt cup or plastic cup of similar or slightly larger size

Marbles or other small weights – enough to fill the cup, over 3 pounds worth

String

Scissors

Scale

2 Chairs

Small blanket or several bath towels

Procedure:

Put the two chairs back to back with a gap between them two thirds as big as the paper is long

placing the chairs

Place the two chairs back to back so they are parallel. The towels are to catch the marbles or rocks when they fall.

Place the blanket or folded towels on the floor between the chairs

Place a sheet of paper across the gap

sheet of suspended paper

A sheet of paper suspended over the gap between the chairs sags down in the center.

Carefully set the cup on the sheet of paper

If the paper stays put, add a marble

fallen sheet of paper and cup

The sheet of paper seemed to fall even before the cup was set on it.

Continue adding marbles until the bridge falls down

Mass the cup and any marbles in it [You may have to pick these up.]

massing the cup

The sheet of paper couldn’t hold even the 11.7 g cup.

Take the sheet of paper and fold it lengthwise so the fold is 1.5 cm

Now make a second fold the other way 1.5 cm

Concertina folds in paper

The folds are made lengthwise to span the gap. If the folds went across the paper, would they change how the sheet of paper acted? Probably not.

Repeat this until the paper is accordion folded [This is called concertina.]

Put the folded piece of paper across the gap between the chairs

concertina bridge

The concertina bridge is straight across the gap between the chairs. The cup sits up on the folds.

Carefully set the cup on the sheet of paper

If the paper stays put, add marbles until it falls down

Mass the cup and marbles

Put four small holes [big enough for the string.] equal distances apart around the rim of the cup

cup with strings

If the four strings are the same length, the cup should be close to level when suspended. This lets the weights distribute evenly and not tip out.

Cut 4 pieces of string about 45 cm long

Tie knots in one end of the strings

Put the untied ends through the holes, one piece in each hole

Tie the ends together [You might want to tape it together too so the knot doesn’t untie.]

Take another piece of paper and roll it up lengthwise so the roll is 10 cm in diameter

Note: The diameters don’t have to be exact. You need a large, medium and small tube.

three bridge tubes

The tube sizes can vary but one is large, one small and one in the middle. A couple of short pieces of tape keep the tubes from unrolling.

Tape the roll so it won’t unroll

Roll another sheet of paper into a 7 cm diameter tube

Roll another sheet of paper into a tube with a 1 cm diameter

Put the 4 cm roll through the string loop of the cup and suspend the cup between the chairs

Empty cup suspended below bridge

The cup is suspended below the middle of the bridge. An interesting comparison could be done putting the cup at different places along the tube. Each attempt would use a new tube of the same size.

Add marbles one by one until the bridge fails

Weight suspended below large tube bridge

Using a wide top cup made it easy to add the rocks. Another advantage was having my hand inside the strings so I caught the cup as it fell before the rocks were scattered over the towels.

Mass the cup and marbles

mass held up by the large tube bridge

The large tube bridge held 478.3 g, an increase of 75.4 g over the concertina bridge.

Repeat this with the 2 cm and 1 cm tubes

Observations:

Describe how the sheet of paper looks suspended between the chairs

Mass of cup and marbles the sheet of paper held up

Describe how the concertina or folded paper looks suspended between the chairs

concertina bridge starting to fail

A single additional rock caused the folds to flatten under the cup. The concertina bridge did hold several more rocks before crashing down to the floor.

Describe what happens to the concertina as you add marbles to the cup

Mass of cup and marbles the concertina held up

Describe how the 10 cm tube acts before and as you add marbles to the cup

Mass of cup and marbles the tube holds up

Describe how the 7 cm tube acts before and as you add marbles to the cup

Mass of cup and marbles the tube holds up

mass held by the medium tube bridge

The medium tube bridge held up 699.7 g which was 221.4 g more than the large tube.

Describe how the 4 cm tube acts before and as you add marbles to the cup

Mass of cup and marbles the tube holds up

Conclusions:

Compare how the plain sheet of paper and the concertina looked suspended.

Where was all the force from the cup focused on the sheet of paper?

Where was all the force from the cup focused on the concertina bridge?

Note: Think about how the tops and bottoms of the folds act.

How is the force from the cup focused with the tubes?

flattening tube

Adding rocks to the cup below the large tube bridge caused the tube to flatten.

What happens to the tube bridges to make them fail?

What do you think would happen if you could make an even smaller diameter tube?

How do you think the forces would focus if the tube were a solid cylinder?

Why is a hollow tube stronger than a solid cylinder?

 

What I Found Out

I didn’t have enough marbles so I went out to the creek and gathered pieces of gravel about the size of marbles.

The sheet of paper barely stayed up suspended between the chairs. It bowed down in the middle. The 11.7 g cup never really sat on it before the paper fell to the floor.

After the sheet of paper was folded into the concertina, it went straight across between the chairs. It did not sag. The cup sat on it as though it was on a table.

massing the weights from the concertina bridge

The only difference between the sheet of paper and concertina bridges were the folds yet the weight capacity increased a lot.

I started adding rocks. Finally the folds buckled under the weight. A few more rocks and the concertina fell. It held up 402.9 g of cup and rocks.

All the force of the cup was in the middle of the sheet of paper and it couldn’t hold it up. The folds of the concertina bridge let the force push and pull between the top and bottom of the folds. The folds carried a lot of the force away from them to the chairs. This let the concertina carry weight until the folds finally broke. Then the force was more in the center and it fell down.

The tube bridges acted much the same but the small tube took longer to change. They were straight across the gap. As the rocks were added, the tubes began to flatten. As the tube bridges failed, the tubes crushed.

The force of the weight is spread around the tube bridge and passed on to the chairs. As the tube collapses, more of the force is concentrated on the middle where the strings are. When the tube fails, all the force has moved to where the strings are crushing the tube and making it bend.

weight suspended from small tube bridge

I did have some more rocks but couldn’t get them to stay on the pile. The tube had started to flatten so the small tube bridge was approaching its weight capacity.

The smallest tube had not failed when the cup was filled to overflowing with rocks. Perhaps I could have added some small lead wheel weights at the beginning so the tube would fail.

An even smaller diameter tube should hold more weight as long as the center is hollow. This lets the force of the weight move away from where the strings are hanging and go into the chairs. The forces on a solid tube would stay mostly where the strings are hanging putting the weight on the bar there until the bar would break.

Physics 25 Stable or Unstable

In some states like Montana with lots of high winds, there are signs warning van drivers to stay off the roads when the winds are blowing hard.

Race cars are built low to the ground to go around corners at high rates of speed. Other vehicles going around a corner too fast will tip over.

An object balances at its center of gravity. So, if the center of gravity is over the object’s base, it should be stable and just stand there, right?

project materials

Question: Why do objects fall over?

Materials:

Roll of quarters [40 quarters]

Pieces of 1 x 2 of various lengths, at least six pieces [I used 2”, 4”, 6”, 8”, 10” and 12”]

Procedure:

Stack the quarters in a straight stack

stable stack of quarters

The tall straight stack wasn’t quite straight but close. The blue dot shows where the center of gravity is.

Push the stack in the middle until it falls over

fallen stack of quarters

When the tall straight stack of quarters fell, only the top half from where the pressure was applied fell. The rest of the stack remained standing.

Stack the quarters so each quarter is slightly [the width of the edge ridge] over from the one below it

leaning stack of quarters

The blue dot shows the center of gravity is half way up the stack of quarters and over the edge of the bottom quarter. The stack is stable because it stands but is unstable as a slight push will cause it to fall.

Push the stack from the side it is leaning toward

Restack the quarters as before

Push the stack from the side

Restack the quarters as before

Push from the side it is leaning away from

pushing stack of quarters

Pushing on the leaning stack of quarters shifts the center of gravity quickly so it will fall over.

Stack half the quarters in a straight stack

Push over the stack

stable stack of quarters

The blue dot is in the center of the stack of quarters. Pushing the stack is making the center shift.

Restack the quarters and lean the stack

Push this stack over

Stack the wood pieces so the longest piece is on the bottom and each piece is centered

stable pyramid

The blue dot showing where the center of gravity is is low and centered over the base.

Push the tower from about half way up the side until it falls over

Stack the wood pieces in the same order but with all the pieces evened up on one side

stable stack

The blue dot shows where the center of gravity is in the center of the stack. It is low and over the base.

Push the tower from about half way up until it falls over

Stack the wood pieces so the shortest piece is on the bottom centering each piece

Push the stack from about half way up until it falls over

Observations:

Draw each kind of stack and put a dot where the center of gravity is

Describe how the stack of quarters acts as you push it over:

pushing tall straight quarter stack

It took a lot of pressure to shove the quarters over off the tall straight stack of quarters.

Straight tall stack:

Leaning tall stack:

Against the lean:

Sideways to the lean:

With the lean:

Straight short stack:

pushing small leaning quarter stack

The short leaning stack quickly overbalanced when pushed with the lean. Unlike the straight stack, most of the quarters tipped over not just the top of the stack.

Leaning short stack:

Describe how the wood stack acts as you push it over:

Centered, longest on bottom:

Longest on bottom, flat side

tipping wood stack over

The center of gravity shifted easily when all the blocks were lined up on one edge so the stack tipped over.

Centered, shortest on bottom:

Conclusions:

Where is the center of gravity for each of the stacks, quarters and wood, you built?

Note: Remember how the spoon balanced so your centers of gravity work for the height, width and depth of each stack.

A stable object will stand by itself. Are your stacks of quarters stable?

pushing leaning stack

Pushing against the lean on the leaning stack of quarters first moved the quarters over the base of the stack then over to where they would fall.

An unstable object may stand by itself but is easy to push over. Are any of your stacks of quarters unstable?

What happens to the center of gravity as you push a stack over?

Does the size of the base of the stack of wood affect how stable the stack is? Why do you think this?

How does the center of gravity change as you push over the stacks of wood?

Is it easier to push over a stack with a high center of gravity or a low center of gravity?

Is it easier to push over a stack with the center of gravity square over the base of the stack or when the center of gravity is off center?

How does the center of gravity determine how stable or unstable an object is?

Can an object be both stable and unstable? Why do you think this?

Why is a car more stable going around sharp curves than a van?

 

What I Found Out:

It was difficult to stack the 40 quarters into a straight stack. Once they were stacked, they didn’t want to fall over. The stack didn’t fall over until I pushed half the stack sideways half way off the stack. This stack was stable. The center of gravity was in the center half way up the stack.

The short stack of quarters was much easier to stack. It was even harder to push over. I had to push the top half more than half way off the stack before it fell over. The center of gravity was in the middle half way up the stack making the stack very stable.

The tall leaning stack of quarters acted differently pushed from the different directions. Pushed from the leaning side the quarters first moved to make a straight stack then fell over the same way as the straight stack. Pushed from the side the quarters acted the same way.

Pushing the stack in the direction in which it was leaning was easy. Almost the entire stack fell over quickly.

The center of gravity was not in the center of the stack. It was moved toward the lean but still half way up. The leaning stack stood up by itself so it was stable to start with but it was unstable too as it would fall over easily.

The center of gravity moved in the direction I pushed the quarters. The stacks fell over when the center of gravity got too far over from the center of the stack.

pushing pyramid over

The regular wood pyramid was very difficult to tip over. The pieces had to be pushed all the way off the ones below before falling. This was a very stable arrangement.

The pyramid stack of wood was very difficult to push over. I had to shove all the pieces off the bottom piece to make them fall.

Even when the edges were in a straight line the boards did not want to fall over until I shoved the boards farther over. It was easier with this stack than with the other stack.

The stack with the big pieces on top was easy to push over. Pushing the top piece an inch made the stack tip over.

The stack of wood with the biggest pieces on the bottom had low centers of gravity. They were very stable. The other stack had a high center of gravity and was unstable.

tipped over inverted pyramid

When pushed, the inverted wood pyramid easily tipped over with the pieces sliding down to the table.

The size of the base did seem important as the pieces had to be pushed off of it before falling. I think I should try different stacking arrangements to see if the base is that important.

Stability seems to depend on the center of gravity as well as the size of the base of an object. Objects with higher centers of gravity are not as stable as those with low centers of gravity. Small bases make it easier to shift the center of gravity and make an object fall over.

Cars have wide bases and low centers of gravity making them very stable. Vans can have wide bases but their centers of gravity are much higher and putting luggage or air conditioning units can make the centers go even higher. Like the two wood pyramids, the van is stable unless going around a corner too fast when the center of gravity shifts making it fall over.