Work, Energy and Power Work refers to an activity involving a force and movement in the directon of the force. A force of 20 newtons pushing an object 5 meters in the direction of the force does 100 joules of work. Energy is the capacity for doing work. To do 100 joules of work, you must expend 100 joules of energy.
Power is the rate of doing work or the rate of using energy, which are numerically the same.
The change in the kinetic energy of an object is equal to the net work done on the object. This fact is referred to as the Work-Energy Principle and is often a very useful tool in mechanics problem solving. It is derivable from conservation of energy and the application of the relationships for work and energy , so it is not independent of the conservation laws . It is in fact a specific application of conservation of energy. However, there are so many mechanical problems which are solved efficiently by applying this principle that it merits separate attention as a working principle.