very day children around the world are encouraged by their parents to go outside and play to burn off some energy But in the world of physics energy is described in terms of work not play In phys ics energy equals the ability to do work Truth be told work means something a bit different to physicists than it does to the average person In their vocabulary work is not just doing tasks and keeping
INTRODUCTION busy For work to be involved there has to be some kind of force that causes an object to move Mathematically if the object is moved in the same direction as the force this is described as W F s work equals force times the distance represented by s moved In other words work is measured by how strong the force is and how far the object moves The more work done on an object the more energy it
ENERGY Making this concept even more inter esting is the fact that energy is not just one thing There are different types of energy The earlier idea of children playing comes in handy when describing the forms of energy For instance there is kinetic energy which is the energy associated with motion Running from third base to home plate while playing baseball is a good example of kinetic energy So are riding a bike and swimming in a pool Then there is potential energy This occurs when an object is positioned in such a way that its energy will increase once it is forced into motion In other words the object has energy because of its potential for movement On the playground a swing set provides an excel lent example of potential energy Pushing a swing puts it in motion creating kinetic energy But at the height of its motion when in a position to be pulled in a downward are by gravity the swing has potential energy Likewise a child sitting at the top of a slide has potential energy before he or she glides down its surface to the ground Kinetic and potential energy are the two most basic forms of energy but there are others Chemical energy is present
INTRODUCTION whenever atoms are combined to form mol ecules which make up the cells of every living thing It is the chemical energy stored in a child's muscles that enable him or her to push a swing or run around a baseball diamond As a bat or tennis racket strikes a ball it gives off heat energy Radiant energy is released by the Sun that shines make ing outdoor play possible while electrical energy is contained in bolts of lightning during a thunderstorm that sends everyone scurrying inside Another interesting fact about energy is that it has the ability to change from one form to another As mentioned before a child sitting on top of a slide has potential energy That potential energy turns to kinetic energy as soon as he or she begins sliding down Within an energy system a group of objects that transfer energy back and forth among themselves energy may move from one part to another but the total amount of energy in the system does not change Studying physics certainly is not child s play meaning it is not simple or unimport ant But with a little imagination the idea of children playing can help make the concept of energy come
