As Homer Simpson once said, “In this house, we obey the Laws of Thermodynamics!” And we do the same thing here at the Children’s Museum of Houston! To summarize the First Law of Thermodynamics, energy can neither be created nor destroyed, only changed (also known as the Law of Conservation of Energy). Basically, it means you can’t have energy magically appear in a system; it has to come from somewhere. Here’s a little experiment that helps demonstrate this idea:
What To Do:
Get a bamboo skewer (available at most supermarkets) and cut off the pointed end. You can also use a 1/8″ wooden dowel cut to about 12 inches.
Duct tape a rubber band to one end of the skewer. I do suggest duct tape, as masking and scotch tape won’t hold as well.
Cut a drinking straw in half.
Thread the other end of the skewer (the one without the rubber band) through one piece of the straw.
Duct tape the other end of the rubber band to the straw.
Place the un-taped end of the skewer onto a table, pull the straw down, and then let go. It should go flying!
CAUTION: Do not point it at anyone including yourself when you let go.
A stretched rubber band has potential energy. Potential energy means energy that is stored until ready to be transformed into a different type of energy. In this case, the stretched rubber band wants to return to its original shape, so that is what creates the potential energy.
When you let go of the toy, the rubber band snaps back, transforming the potential energy into kinetic energy (energy in motion). That kinetic energy generates the force needed to lift the toy off the table. The more you stretch the rubber band, the more potential energy is available to transform into kinetic energy.
Now some people may say that the potential energy didn’t come from anything, so wasn’t it created? Nope, sorry! That potential energy came from the kinetic energy you used to stretch the rubber band in the first place. And that energy came from the chemical energy stored in the food you ate. And so forth and so on.
Thanks to Eneergcam for his Fun Jumpers Instructable that inspired this video!