In several of our previous programs, the G3 scientists had a chance to loosely touch on the science of “energy.” But for this program, all of our attention was fixed on “energy” – in particular, the difference between kinetic energy and potential energy. Before we got to the hands-on fun, we needed to first understand some basic information about energy. What is it? If you were asked to describe energy, what would you tell someone?
Perhaps one of the simplest definitions of energy is that energy is the ability or capacity to do work. And what is work? Work is done when something, regardless of size, moves. In other words, energy is needed to cause motion. Energy itself is generally divided into two categories: Kinetic and Potential. Potential energy is stored energy that is waiting to work. If you were to stretch a rubber band, but not release it, that rubber band would be holding potential energy. You might be surprised to learn that potential energy can be found in many forms – chemical, mechanical, nuclear, gravitational, and electrical. Gasoline, for example, is a chemical form of potential energy. Other examples of potential energy are a cell phone, a car battery, and a ball sitting motionless on a table. Think back to our first program on catapults for another example of potential energy. When we pulled the lever (or spoon) back, stretching the rubber band, we created potential energy in the spoon that transformed into kinetic energy when we released the spoon and let the marshmallows fly!
Kinetic energy, as you may have guessed, is essentially the opposite of potential energy. A good definition might be that kinetic energy is energy in motion that is actually doing work. A baseball being thrown is experiencing kinetic energy. So is a person bicycling down the road. Where gasoline in a can is an example of potential energy, the fire that gasoline creates would be an example of kinetic energy. A ball sitting motionless on a table is a good example of potential energy; when the ball begins to roll along the surface, it exhibits kinetic energy. Just in case you need some more examples to understand the difference between potential and kinetic energy, the youtube video below (from user “angiesparks”) should help. The song is sort of silly (but very catchy!)…and it will definitely help you distinguish between the two types of energy! [The song is “Kinetic and Potential Energy” by Tom Glazer and Dottie Evans from the Singing Science Records.]
You would be amazed at the number of places you can find examples of energy; anywhere you see motion there is energy. Even in your favorite movies! For fun, the G3 scientists watched a segment from the movie Hoodwinked. Uploaded to youtube by user “BobChlly,” this video points out examples of both kinetic and potential energy that you may have missed when you first watched the movie…
Before we jumped into our own project for the afternoon, it was time for a few fun energy demonstrations of our own. First, Nicole pulled out the one and only Slinky! The Slinky, which has been around since the 1940’s, provides an excellent example of potential and kinetic energy. When a slinky is sitting at the top of a set of stairs at rest, it is holding potential energy; as soon as it starts to “walk” down the stairs, it is experiencing kinetic energy. With a homemade set of stairs created from a stack of empty paper boxes, each G3 scientist got to try their hand at getting the slinky to shift from potential to kinetic energy 🙂
Next, we watched a demonstration of the “magic rollback can,” as created by the instructions on Steve Spangler’s Science web site. With just a few simple items – coffee can, 9-volt battery, rubber band, some tape, some paperclips – you can create a magic rollback can of your own. What is the “magic”? If you roll the can away from you, it will eventually stop in place and roll back to you! How does this work? The battery, which is suspended in the middle of the can by the rubber band, helps to create potential energy by causing the rubber band to wind and twist itself up when you first roll the can. Eventually, the can reaches its maximum potential energy, the rubber band begins to unwind, and the can rolls back to you using kinetic energy.
But our main goal for the day was to create our very own “wind-up racers.” Once again, Steve Spangler gave us the instructions we needed to build our racers. And they were fairly easy to put together – most of the G3 scientists had them assembled before I even finished with the instructions (minus a few early mishaps with threading the rubber bands through the wooden spools). And then the testing began! What our scientists quickly discovered is that the rubber bands – which were the key to creating potential energy and later releasing kinetic energy – were over-stretching after a handful of test runs. In other words, the rubber bands were either became so loose and overstretched that it was difficult to store enough potential energy for the racer OR they were actually becoming some weak and overstretched that they actually snapped! Thus, there was a lot of repair work going on during our testing phase of the racers. But not easily defeated or disappointed, our scientists simply reassembled the racers with new rubber bands.
During our show-and-tell, the G3 scientists proudly displayed their racers – some decorated quite uniquely, and all with interesting names – and described how their testing went. Several noted that their racers would start off by just spinning in a tight circle before they moved in a wider arc along the floor. Everybody noted that their racers moved in a curved path versus a straight path (probably due to the position of the pencil that is used to wind-up the rubber band). Regardless of the result, even though we didn’t have time to actually do any races against each other, all of the G3 scientists enjoyed creating and modifying their own racers…and Nicole made sure that everyone went home with a fair share of extra rubber bands for repairs! 🙂
DUE TO CONSTRUCTION AT CHESHIRE PUBLIC LIBRARY, OUR PROGRAMS SCHEDULED FOR JUNE 2012 HAVE BEEN CANCELLED 😦 However, if all goes well, we will back in business for a full schedule of programs in July. Be sure to check back at the library for more information as we move through June…