What Is energy Energy is another word for power or the ability to do work Energy makes things move It makes machines work Energy also makes living things grow The sun is the source of almost all energy on Earth The sun makes plants grow When humans and animals eat the plants they gain energy from the chemical energy that is stored in the plants Humans get energy to move and run from eating food Energy exists in many different Plants and people need energy People get it from the food they eat while plants get it from the sun 4
Pushing pedals to make a bike move is a form of mechanical energy Vocabulary An atom is a tiny particle Atoms are the building blocks of all matter forms Electrical energy is used to power televisions and computers This energy is created when particles called electrons move from one atom to another Heat and light are also forms of energy A dog’s bark is an example of sound energy The energy that an object or a body holds because of its motion and its position is called mechanical energy Humans and machines use mechanical energy to do work 5
PotentIal and KInetIC energy Each of the different forms of energy can be described as either potential energy or kinetic energy Potential energy is stored energy For example the chemical energy of food is stored energy When people eat their bodies change the stored energy into moving energy Potential energy can also come from the position of an object For example a rock on top of a hill has potential energy because it could roll down the hill Kinetic energy is moving energy This large rock is balanced on a hilltop The rock has great potential energy 6
Once the rock starts rolling down the hill it gains kinetic energy and loses potential energy Electrical energy is kinetic energy because it consists of tiny particles called electrons that move from one atom to another These windsurfers are using the kinetic energy of wind to propel them forward Think About It A player lifts a bowling ball takes aim and rolls it down the alley The ball strikes all ten pins Is this an example of potential or kinetic energy or both 7
