Kinetic energy

Kinetic energy is the energy an object has because of its motion.

  • Objects move or change direction when a force is applied to them.
  • In physics, this process is said to involve ‘work’, so work is done whenever a force moves an object.
  • This application of force by one object to another involving work being done and results in kinetic energy being transferred from one place or one object to another.
  • Everything in the universe has kinetic energy because everything above absolute zero is in motion.
  • Planets moving through space, cars and people all contain potential energy and kinetic energy.
  • Kinetic energy is evident at an atomic scale as molecules vibrate when heat is applied to a substance, electrons move around an electrical circuit or light illuminates a room.
  • The human senses of sight, hearing and touch are tuned to different forms of kinetic energy.

An example of this might involve a person forcing a heavy bolder to roll up a hill. By the time they reach the top they feel exhausted by the effort because they have used up a lot of kinetic energy some of which has been transferred to the boulder. This energy might then be transferred to other boulders if it crashes back down the hill.

If the observer in this example is too heavy and doesn’t move, no energy is transferred to it. Work is still done but this time the energy is transferred between the person’s muscles etc. and released into the air in the form heat.