Kinetic energy, potential energy and the ‘magic can’

I really enjoy doing science projects that make people think! The puzzled looks on the face of the students I see continually drives me to find more and more of these unique projects to get them thinking. This week, I thought I would share one with all of you to keep you wondering, ‘how did that work?’ Let’s get started!

*Remember to ask an adult before doing this experiment.

Materials

- empty coffee can with a lid - drill - hex nut - several really long rubber bands

- flat surface to experiment on

- twist tie - masking tape - craft sticks/popsicle sticks

Procedure

1. With the masking tape, cover the sharp edges of the coffee can. You do not want to cut yourself.

2. Put the lid on the empty coffee can. With the help of an adult, have them drill one hole in the middle of the lid.

3. Repeat on the bottom of the can.

4. Measure a rubber band to ensure it is long enough. Hold it up to the can; you want it to be long enough to go from one end of the can to the other.

5. This is a bit tricky; you will now have to feed one end of the rubber bands through the hole in the bottom of the coffee can. Do not go all of the way through, you want a bit sticking out. Stick the craft stick through the small end of the rubber band that is still sticking out. This is to hold the rubber band in place. 6. Repeat with the lid. 7. Wrap the twist tie around the hex nut. Leave the ends of the twist tie sticking out on opposite sides.

8. Take one of the ends of the twist tie and loop it around the rubber band coming in from the bottom of the can.

9. Hold the lid close, but not closed and secure the other end of the twist tie to the rubber band coming from the lid. 10. Put the lid on the can. 11. Place the can on the floor and gently roll it away from you.

12. Observe what happens!

What is going on?

Did you know that energy comes in many forms? The “magic can” works as a result of both kinetic and potential energy. Kinetic energy is a form of energy in motion. Stored energy on the other hand is also known as potential energy. When you push the “magic can,” you give it kinetic energy as it starts to roll away from you. The hex nut hiding in the can holds one of the rubber bands in place while causing the other one to twist and turn, winding itself up inside. The can will continue to roll away from you as long as it is winding up the rubber band. Once there is no more room on the rubber band to twist up, it stops. This is where the kinetic energy becomes potential energy. As the rubber band unwinds on the way back to you, the potential energy again becomes kinetic energy.

Patty Rooks is senior scientific consultant at PRAXIS, “Connecting Science To The Community.” Contact Praxis at praxis@praxismh.ca, www.praxismh.ca, Tweet or follow us @PraxisMedHat, or friend us on Facebook.