The figures below illustrate these points. Now we are ready for a definition of energy. Energy is defined as the ability or capacity to perform work. It should be clear that there must be some relationship between work and energy. First it would be useful to mention various forms of energy.
Kinetic energy is energy associated with motion.
Two examples of bodies possessing kinetic energy are a thrown ball and a moving car. Note that since the kinetic energy depends on both the mass and the velocity, it is possible for a very massive object moving at a small velocity to have the same, or more kinetic energy as a less massive object moving at a high velocity. Potential energy is energy associated with position . If the rope is cut, the object loses potential energy because it loses height as it drops. Notice also that this potential energy is converted to energy of motion, or kinetic energy , as the object falls.