The energy of a moving object
Anything that is moving can be made to do work on something else simply by running into it. That capacity has a name.
Kinetic energy
The energy an object possesses because of its motion is called kinetic energy.
You have seen it do work already
In each of these, something moving does work on something that was not moving.
- A hammer moving onto a nail drives the nail into the wood.
- Wind moving against a sail pushes a boat along.
- Flowing water turns a water wheel.
Stop the motion and the energy is gone
Kinetic energy is not a substance carried inside the object. It exists only while the object is moving, which is why bringing something to rest is exactly the same event as taking all its kinetic energy away.