Physics

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Materials

• 1 heavy spool (a sewing thread spool is way too light - a spool full of steel wire is perfect!)
• 1 toothpick
• 1 thick rubber band, just a bit longer than the hole through the spool (if you have a very wide spool you can tie two rubber bands together)
• 1 washer
• 1 pencil
• 1 pair of scissors
• Tape
• Safety equipment: 1 pair of safety goggles

Explanation

When you spin and stretch the rubber band, energy gets stored in it. This energy is called potential energy, because when it is "released" it has the potential to carry out work. The more you wind, the more potential energy is stored in the rubber band. When you release the toy, the potential energy is released through the untwisting of the rubber band. The potential energy is then converted into kinetic energy of the toy.

The kinetic energy of the toy is then slowly converted by friction into thermal energy (heat) of the air and the floor. This causes the toy to eventually stop.

Experiment

You can turn this demonstration into an experiment. This will make it a better science project. To do that, try answering one of the following questions. The answer to the question will be your hypothesis. Then test the hypothesis by doing the experiment.

• What happens if you use a thicker rubber band?
• What happens if you use a longer rubber band?
• What happens if you twist the rubber band more times?
• What happens if you use a new, "fresh", rubber band?
• What happens if the toy rolls on a carpet?

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