2008-12-12 / Columnists

Drawing On Science For Kids

Energy
Commentary By Stephen S. Yaeger

All living things use energy. Early man most certainly realized that energy (he may not have had a word for "energy") was something important. Perhaps it was fire …. the heat it produced … that kept him warm and made his food taste a bit better. Maybe it was the club he used to bring an animal down. Perhaps he realized that the higher he held his club the more damage it did when he brought it down. If it weren't for our understanding of energy our lives would be much different today. So what exactly is energy all about?

Energy is the ability or capacity to do work as the result of a change in matter. The change can be physical. Think of the club of early man. It may be chemical. Think of what happens when you strike a match. There are many forms of energy. Let's take a look at them and an example for each.

Heat energy: burning wood Light energy: the sun's rays Mechanical energy: a motor Sound energy: a lion's roar Magnetic energy: horseshoe magnet Electrical energy: powers your TV Chemical energy: storage battery Atomic energy: combining or

splitting atoms

Energy can be classified depending on whether it is inactive or active. Potential energy is energy that is stored. It is not yet being used so it is inactive. When a pitcher brings his arm back ready to throw the ball it has potential energy. Kinetic energy is active energy or energy of motion. When the pitcher moves his arm forward releasing the ball, the ball is in motion and has kinetic energy. Depending upon the pitcher's ability, the potential energy and resulting kinetic energy of the ball will vary. A strong-armed pitcher will, of course, store more potential energy in the ball and result in a higher kinetic energy than a weaker-armed pitcher.

So you see that potential energy can be converted into kinetic energy. The reverse is true also. Imagine yourself on a swing. At the forward high point you have potential energy. As you swing downward your potential energy is converted into kinetic energy. When you reach the backward high point your kinetic energy has been converted back into potential energy. Again, as you swing downward your potential energy is converted back into kinetic energy. Of course, if you don't do anything to your swinging, in time your potential energy decreases and so does your kinetic energy.

Scientists soon discovered that energy is governed by physical/chemical limitations. This is known as the Law of Conservation of Energy. The law states that under ordinary conditions, energy can neither be destroyed nor created. Energy can only be converted from one form into another. For example, moving water is used to turn a turbine to produce electricity that is directed to your house. You switch on a lamp and your radio in your room to do your homework. The moving water is kinetic energy, which is converted into mechanical energy to turn the turbine. The rotating turbine produces electrical energy, which you convert into light energy when you switch on your lamp. The light energy is converted into heat energy and the radio produces sound energy as a result of its use of electrical energy. The light energy from your lamp is converted to chemical energy by the plant on your desk to make its own food. Questions/comments? E-mail Steve: Drawingonscience @aol.com

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