Energy is Everywhere What’s invisible but all around you What is found in the tiniest of particles and the largest galaxy What powers cell phones makes your muscles flex and no matter how much it’s used or changed never truly disappears When you see the word energy you may think of how you feel tired or wide awake when you get up in the morning Or perhaps it makes you think of terms such as solar energy or nuclear energy But energy is much more It’s energy 4
Energy is inside food batteries and light it’s in rubber bands and flowing water Since it cannot be created nor destroyed it’s continually being transformed and moved Though you can’t usually see it with your eyes energy is all around you It’s what makes things move creates noise and heat It lights your way and helps you play Energy is everywhere Batteries Flowing Water Got Phlogiston About 300 years ago philosophers we call them scientists today thought the universe contained four kinds of matter and when they were burned a special substance called phlogiston remained Scientists tried to demonstrate its existence by burning objects or elements and weighing what was left It wasn’t until hydrogen which can burn leaving little residue was discovered that scientists decided phlogiston was not exactly an actual substance but a principle or established truth Eventually scientists called it energy instead 5
What is energy exactly Energy is the capacity of a physical system to perform work A system is a portion of the universe chosen to see how varying conditions change it A system may be complex such as a human body or simple like a pinwheel spinning in the wind Work is a force acting on an object to move it It can be observed in one way or another but something must move to be part of work When you pick up a glass your hand and arm muscles are doing work When wind blows on a pinwheel its work makes the pinwheel spin I’m Not Playing I’m Working Though it can take effort to sit and listen to someone talking it’s not considered work unless something is moving something else Traveling in a car is not work since it’s the car’s engine that is turning the drive shaft not you But playing sports is considered work since that involves movement So next time someone says Get to work maybe it’s time to go out and have some fun 6
Energy Waiting to Happen Energy exists in two basic forms potential energy and kinetic energy Potential energy is stored energy It can be stored in large visible objects or inside atoms too small to see The most common potential energy works constantly on everything on Earth When you pick up your shoes you sense weight because gravity pulls on them They contain gravitational potential energy It comes from gravity’s effect on all objects on Earth It increases as the object gets farther from our planet’s core Work at Play When you swing on a swing you increase your gravitational potential energy by pumping your legs Building that potential energy takes work When you swing down you have to work to build up potential energy again 7
