# Fast and Easy Science Fair Projects: Flying in Circles

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Scissors
Metal Washers (2)
Standard size sheets of typing paper
Pencil
Plastic trash bag
Thin string

## Air friction: Sometimes good, sometimes not

Purpose: Set up some demonstrations showing how air friction (resistance) affects falling abjects.

Overview: When we see or hear the word "friction: we usually think about it taking place between two surfaces. As project 4 explained, friction is the resistance to motion when two things rub together. Friction can also occur, however, between air and any object that moves through it. Air friction causes resistance, which pushes against the object.

Car manufacturers try to design cars that are "Streamlines," which means the cars are shaped to let air flow smoothly around them because it then takes less energy to move the car. This saves on fuel. The car will get more "miles (or kilometers) per gallon" - go farther on less gasoline at the fuel pump, and the car will also put less pollution into the air.

Designers of aircraft, just like the designers of cars, try to make their crafts have as little resistance to the air as possible, but sometimes, air friction is desirable. When sky divers jump out of an airplane, the parachutes need to have a lot of air resistance to slow their descent and land them safely to the ground.

Hypothesis: Air friction can be increased and decreased simply by changing an object's shape.

You need:

• Plastic trash bag
• 2 metal washers
• 2 standard size sheets of typing paper
• Scissors
• Pencil

Procedure: First we'll compare how air friction affects two sheets of typinf paper, keeping the material and height Constant and shape the only Variable. Fold one of them into a paper airplane and crumple the other into a ball. Stand in a clear area in a room. Stretch your arms out to your sidesm holding the airplane nose down in one hand and the paper ball at the height of the airplane nose in the other. At exactly the same time, drop them.

Next, with a scissors, cut the section of plastic the size of a sheet of paper out of the plastic bag. Tke a pencil or nail and carefullt poke a small hole near the edge of each corner. Cut four pieces of thread or thin string, each 2 feet in length. Tie one end of each pieve to each hole in the plastic. Tie the loose ends of four threads to a metal washer. The washer is our sky diver, and the plastic bag is his parachute.

Now, cut another piece of plastic the same size, put a washer inside and wrap and tie it into a bundle using 8 feet of the same thread or string. Holding the parachute and wrapped plastic out so they are the same height from the floor, let them go. Here afain, shape is the onl Variable.

In order to really demonstrate the difference streamlining makes, do one more drop. In one hand, hold your sky diver. In the other hand, hold the paper airplane, wit h its nose facing the ground. Out-stretch and raise your arms so the bottom of the sky diver is the same distance from the ground as the nose of the airplane. Let go of both objects at the same time. Does the sky dover's parachute encounter much more resistance, from friction with the air, than the streamlined paper airplane?

Results and Conclusion: Write down the results of your experiments. Come to a conclusion as to whether or not your hypothesis was correct.

Something more: Would it make a difference if the shape of the parachute was square or round instead of rectangular? Would another shape have even more air resistance?

## More by this Author

Bellarina 5 years ago

That's suppose to be show picture step by step.

OmarV 4 years ago

i love u but this thing sux!!!