# Physics 2 Combining Forces

Last week we found out pushing and pulling were contact forces and gravity is a non-contact force. Having more than one force can change how an object moves.

Question: How can we show how forces add up?

Materials:

3 sheets of paper

Fan

Tape

Procedure:

Open your Journal and write Project 2

Hold a sheet of paper up as high and flat as you can

For this Project I held the sheet of paper out flat. How would holding it on the edge change how the paper fell? What would cause this change?

Drop the sheet of paper

Describe how the sheet of paper falls to the floor

Turn on the fan

Drop the sheet of paper like before but standing in front of the fan

Describe how the sheet of paper falls to the floor

Turn off the fan

Crumple the paper into the tightest ball you can

A paper ball has all the weight of the sheet of paper pushed together so it doesn’t catch the air and falls quickly to the floor.

Hold the paper ball up high and drop it

Describe how the ball falls to the ground

Turn on the fan

Hold the ball up like before and drop it in front of the fan

Describe how the ball falls to the floor

Fold a piece of paper into the first paper airplane (Directions are below.)

Airplane 1 has big wings with a short steep nose that doesn’t go through the air very well.

Fold a piece of paper into the second paper airplane.

Fly both paper airplanes several times to find out how and how far each kind flies

Airplane 1 has big wings. Throwing it the wings hold it up but it doesn’t fly forward well instead it acts more like the sheet of paper and settles down to the floor.

Turn on the fan

Fly each paper airplane toward the fan several times to find out how and how far each kind flies toward the fan

Throwing airplane 1 at the fan makes the airplane turn aside.

Fly each paper airplane away from the fan several times to find out how and how far each kind flies away from the fan

Airplane 1 is clumsy with its large wings but the wings catch the air from the fan and it floats farther until the breeze is mostly gone dropping the airplane to the floor. This is when the force of throwing the airplane and the force of the air add up.

Observations:

Describe how the sheet of paper falls to the floor

1) Plain

2) In front of the fan

A sheet of paper has a big surface to catch the air blown by the fan.

Describe how the ball of paper falls to the floor:

1) Plain

2) In front of the fan

Describe how the airplane flies without the fan blowing

Airplane 1:

Airplane 2:

Describe how the airplane flies toward the fan

Airplane 1:

Airplane 2:

Airplane 2 hits the air from the fan and turns aside. The force of the air goes against the force of throwing the airplane.

Describe how the airplane flies away from the fan

Airplane 1:

Airplane 2:

Conclusions:

Why does the sheet of paper fall to the ground differently than the paper ball?

How does the fan change how the sheet of paper and paper ball fall? How do you think the fan does this?

Is this a contact or a non-contact force? Why do you think so?

Why do you think the second airplane goes down nose first?

Airplane 2 has a long nose and small wings. The weight of the nose pulls the airplane down. It flies longer if it is thrown harder.

Why do the airplanes turn aside when flown at the fan?

What do you think would happen if the fan was much bigger so the area of blowing air was bigger?

Why do the airplanes fly farther when flown away from the fan?

Which airplane is more like the sheet of paper? Why do you think so?

Which airplane is more like the paper ball? Why do you think so?

What I Found Out:

The sheet of paper didn’t fall straight to the ground. It settled going a little to the side then back again getting lower each time. When the fan was blowing the sheet of paper blew across the room as it fell to the floor.

Compare a paper ball with a sheet of paper. Which will catch more air? Why? Yet even a paper ball catches some air from the fan as it falls.

The paper ball fell straight to the ground much faster than the sheet of paper fell. When the fan was blowing, the ball seemed to fall even faster but moved a little ways away from the fan.

A sheet of paper is flat and big. A paper ball is much smaller and sort of round. The sheet of paper floats on the air so it falls slowly compared to the paper ball that falls through the air.

The fan makes the air move and push on the paper. The sheet is large and flat so it catches a lot of moving air and moves a lot. The paper ball only gets pushed a little but the edge of the moving air might push it down too as it fell faster.

The air is a contact force. I can’t see it but I can feel it pushing. If there was a lot of dust, I would see the air moving.

The second airplane has a long nose and smaller wings. If you fold the wing part down another time when making the airplane the nose would get even longer and the wings smaller. How would this affect how the airplane flew in this Project?

I like making paper airplanes but am not very good at flying them. I had to do this Project at the laundromat because there was a good fan there. I was afraid of throwing the airplanes too hard and hitting someone there. I think they would have flown much better if I had thrown them harder.

The first airplane doesn’t fly very fast. It gets slower as it goes and the back end begins to sink. Then the airplane falls to the ground.

The second airplane flies faster but the nose pulls it down and makes it crash.

Flying toward the fan both airplanes turn around the blowing air. I did finally get the first airplane to fly in the middle. It seemed to stop then go straight down.

Flying away from the fan both airplanes stayed up longer and flew straighter. The first one even seemed to lift higher at first.

Flying the airplane over the top of the fan lets the wings catch the moving air. How would this cause the airplane to fly farther?

The second airplane has smaller wings than the first one. The wings are farther back on the airplane. The nose is long and thick and heavier than the back end of the airplane. Gravity pulls on the long nose and there are no wings to hold it up so the nose falls and makes the airplane crash.

When the airplanes flew at the fan, the air pushed on them. They turned to get away from the push of the air. If the fan were bigger, the airplanes would act like the time I flew an airplane into the middle: they would stop and fall down.

When the airplanes flew away from the fan, the moving air pushed them up and carried them away like it did the sheet of paper. The air slows down as it gets father away from the fan so the airplanes would fall down.

The first airplane was more like the sheet of paper because it had larger wings to catch more moving air. The second airplane had smaller wings so it was mostly folded up tight so it would fall more like the paper ball.

Paper Airplanes

1. Fold the paper lengthwise. Make the crease sharp.

It’s important to make very tight creases for the folds. Use a thumb nail or a coin to make the folds tight.

Open the paper back up.

Fold the top corner down along the crease to make a triangle with one side along the crease.

Fold the paper so the edge is flat along the center fold.

Fold the other top corner down the same way so the paper has a triangle on the top.

This side of the triangle should be the same size as the first side.

Fold the paper back along the crease.

Fold the long side down on one side.

The paper should be folded so the edge is flat along the bottom of the airplane so the wing is folded square.

Turn the airplane over and fold the other long side down the same.

Both wings are now made. The wings need to be about the same size.

Push up these folded pieces until they are flat at right angles to the rest of the paper.

Tape the back ends together.

Tape the nose triangle ends together.

1. Fold the paper lengthwise. Make the crease sharp.

This is the same fold as for the other paper airplane.

Open the paper back up.

Fold the top corner down along the crease to make a triangle with one side along the crease.

The edge of the triangle, like for the other paper airplane must go along the center fold.

Fold the other top corner down the same way so the paper has a triangle on the top.

This triangle folds down along the center fold too. Because this is the second fold, it is harder to make the fold really tight.

Fold both sides to the crease a second time so it looks like a long triangle.

This triangle must match where the same triangle was on the other side.

Fold the paper back up on the original fold.

This fold must be even with the other side.

Tape the nose end together with one piece of tape.

Fold the wing down so the end is flat along the edge of the body fold. Do the same for the other wing.

Fold down the long side on each side.

This paper airplane is now ready to fly.

Push the side flaps up flat.

Tape the back end together with a piece of tape.