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Summer Brain Games

Experiment: Flying Gyroscope

How can a simple plastic tube fly so far? With science! Or more specifically, with rotational inertia. This deceptively simple-looking toy flies a lot farther than expected. How far can you throw it?


One-liter plastic bottle
Utility knife (optional)


  1. You'll need a one-liter bottle with straight (not curved) sides, or at least a three-inch section where the bottle is a perfect cylinder.
  2. Draw a straight line all the way around the bottle near the bottom. Be sure the line is on a part of the bottle that has straight vertical sides.
  3. Poke a hole on the line with the sharp point of the scissors or a utility knife. Cut all the way around the bottle, discarding the bottom.
  4. Measure three inches from the first cut and draw another line around the bottle.
  5. Poke a hole on this line with the scissors or a utility knife. Cut all the way around the bottle, discarding the top. You should be left with the middle piece of the bottle that's a cylinder or tube with straight sides. Use tape to cover any rough edges made by cutting.
  6. Next, you'll tape four pennies on one end of the tube so they are equally spaced apart. Start by taping one penny in place on the inside of the tube using a small piece of tape.
  7. Place the tube on its side and, without creasing the plastic, gently squish the tube and mark the spot on exact opposite of the penny. Tape another penny there.
  8. Place two more pennies on the edge of the cylinder exactly between the two pennies already in place. The distance between all four pennies should be the same. Alternatively, the placement of the pennies can be more accurately determined by dividing the circumference of the tube by four and placing each penny that distance apart.
  9. To fly the gyroscope, hold it like a football. Throw it penny-side forward and give it a spin, the same way a football is thrown. You can also throw it underhand - grab it by the non-weighted end, throw it penny-side first and put a spin on it. It may take you a few tries to get the hang of it! Make sure the gyroscope spins as it flies, that's what will help it travel farther.

What's Happening?

Two things help the flying gyroscope move so well: the shape and the weight from the pennies. As the tube flies through the air, there is very little air resistance caused by its shape - the air goes right through the middle. That reduced friction helps the tube maintain its forward speed. The weight from the pennies affects how it spins. The spinning weight located on the leading edge keeps the gyroscope from tumbling. Imagine throwing a Frisbee without spinning it. It would tumble and fall quickly to the ground. The spinning motion, or rotational inertia, stabilizes it and keeps the Frisbee flat. The spinning weight on the flying gyroscope does the same thing and keeps it stable as it flies through the air.


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