# Physics 3 First Law of Motion

Perhaps you have noticed especially in Project 1 that something sitting on a table or anywhere does not move unless some force makes it move. That can be a contact force like a push or a pull. It can be a non contact force like gravity, magnetism or electricity.

A man named Sir Isaac Newton wrote this down as his First law of Motion:

An object at rest remains at rest as long as no net force acts on it. An object moving with constant velocity continues to move with the same speed and in the same direction as long as no net force acts on it.

Question: How does Newton’s First Law of Motion work?

Materials:

Small car

Meter long smooth board 15 cm wide or car track

Wood block 1 cm x 1 cm x 15 cm (The height should be the height of the car hood.)

Tape

Several thick books

Ruler

Penny and nickel

Procedure:

Open your journal and write the name of the project. Copy the table.

Keeping a Journal of all of the Projects makes it easy to look up previous Projects.

Tape the small wood block across one end of the long board

The block is attached at the end of the board. Why is the block only as high as the car hood? Would a higher block change your results?

Draw a line across the other end of the board 1 1/2 times the length of the car from the end

The starting line is drawn across the board. Why is drawing the line important? Would starting the car at a slightly different place each time change the results?

Put books under the other end of the long board so the line is 10 cm off the floor [I put the line across the edge of the book so it was always in the same place.]

The car rolled down the ramp at 10 cm high then bounced off the block to a stop.

Set your car at the line and let it run down the ramp several times (If your car does not go straight down the ramp, get another car that does go straight down the ramp.)

Balance a penny on the roof of your car, set it at the line and let it go down the ramp

Measure from the block to where the penny lands and record it in the table

The penny flew around 12 cm from the car on the 10 cm high ramp.

(If the coin rolls off, don’t count that trial run but do another until the coin lands flat.)

Repeat this with the penny two more times

Repeat this with the nickel three times

Raise the line to 15 cm off the floor

Repeat with the penny three times

Repeat with the nickel three times

Raise the line to 20 cm off the floor

Repeat with the penny three times

Repeat with the nickel three times

Observations:

Describe what happens when the car alone goes down the ramp

10 cm

Describe what happens when the penny is on the car when it goes down the ramp

Describe what happens when the nickel is on the car when it goes down the ramp

15 cm

Describe what happens when the penny is on the car when it goes down the ramp

The car went faster down the ramp, hit the block at the end and bounced back then went to the block and stopped.

Describe what happens when the nickel is on the car when it goes down the ramp

20 cm

Describe what happens when the penny is on the car when it goes down the ramp

Describe what happens when the nickel is on the car when it goes down the ramp

Analysis:

An average is found by adding the different values (the 3 distances) then dividing by the number of values (3)

Find the average distance the penny goes for each board height

The distance to the penny doubled when the ramp was raised up to 15 cm.

Record the averages in the table

Find the average distance the nickel goes for each board height

Record the averages in the table

Draw a line graph of average distance against board height for the penny and nickel

Conclusions:

What force makes the car roll down the ramp?

The little car really roared down the ramp when it was raised to 20 cm high. It hit the block hard bouncing off the ramp and onto the table.

What force stops the car?

Why don’t the penny and nickel stop with the car?

The penny went over 30 cm all three times when the ramp was raised to 20 cm. It rolled across the table several times too so I had to redo the runs.

Why do the penny and nickel travel differently for the same distance?

Why don’t the penny and nickel travel the same distance all three times?

What stops the penny and nickel?

What do you think would happen if you raised the ramp another 5 cm? Try it and find out.

How does Newton’s First law of Motion apply to your results?

What I found Out

Each time I raised the ramp, the car went faster. The coins went farther for each higher ramp. Gravity pulled the car down the ramp.

When the car went down the first ramp by itself, it rolled faster as it went down. When it hit the block on the end, it bounced back and rolled off the ramp.

The penny sat on the car hood. When the car hit the block, the penny flew out onto the table. The nickel went a few centimeters farther than the penny did.

When the ramp was raised to 15 cm, the car went faster and hit the block harder, bouncing back more. Once it bounced all the way off the ramp. The penny and the nickel went farther too. The nickel still went farter than the penny.

The car went even faster when the ramp was raised to 20 cm. The penny and nickel went farther than my ruler could measure so I had to move the ruler and add the extra.

The block stops the car with a push against it. The penny and nickel are above the block so no force acts on them and they keep going.

The nickel is heavier than the penny so it goes farther than the penny. Even though I tried to start the car at the same place each time, it wasn’t exactly the same so the car ran down the ramp a little differently so the coin flew off differently.

The penny and nickel fall to the table top. Gravity makes things fall so gravity must be what stops the coins from going any further.

I couldn’t raise the ramp higher this time. My car was very flat and the coins slid off the hood. I did use a higher ramp once before. The penny and nickel went into the table top in a short distance because the car was pointed down into the table top.

Newton’s First Law of Motion says an object at rest stays at rest and an object in motion stays in motion at the same speed and direction unless acted on by another force. The car and coin were pulled down by gravity. Gravity made them go faster the longer they went down the ramp.

At the end of the ramp the force of the block stopped the car. No force acted on the coins so they kept going until gravity pulled them down to the table.