What is kinetic energy?
Kinetic energy is the energy an object has because it is moving. The faster and heavier an object is, the more kinetic energy it has.
The formula for kinetic energy is one-half times mass times velocity squared, written KE = ½mv². Because speed is squared, doubling an object's speed gives it four times as much kinetic energy. That is why car crashes at high speed are so much more dangerous than at low speed.
Kinetic energy is often converted from or into other forms of energy. A ball held high has potential energy because of its position. When it falls, that potential energy turns into kinetic energy. When it hits the ground, the energy turns into sound, heat and the energy that makes it bounce.
Kinetic energy in action
Wind turbines capture the kinetic energy of moving air, and hydroelectric dams use the energy of flowing water. Moving vehicles, swinging hammers and running animals all have kinetic energy. Even tiny particles have it: temperature is a measure of the average kinetic energy of molecules.
Did You Know?
The word kinetic comes from the Greek kinesis, meaning motion, the same root as cinema, originally moving pictures.