Potential Energy
Almost every mountain range in the country has a “balancing act”--a boulder precariously perched on top of a hill so that it looks as if a little push would send it tumbling down the slope. If the balancing rock were to fall, it would clearly acquire kinetic energy, and it would do “work” on anything it smashed. The balancing rock has the ability to do work even though it's not doing work right now, and even though it's not necessarily going to be doing work any time in the near future. The boulder possesses energy just by virtue of its position.
This kind of energy, which could result in the exertion of a force over distance but is not doing so now, is called potential energy. In the case of the balancing rock, it is called gravitational potential energy because the force of gravity gives the rock the capability of exerting its own force. An object that has been lifted above the surface of the Earth possesses an amount of gravitational potential energy exactly equal to the total amount of work you would have to do to lift it from the ground to its present position.
We encounter many other kinds of potential energy besides the gravitational kind in our daily lives. Chemical potential energy is stored in the gasoline that moves your car, the batteries that power your radio, and the food you eat. All animals depend on the chemical potential energy of food, and all living things rely on molecules that store chemical energy for future use. In each of these situations, potential energy is stored in the chemical bonds between atoms.
Wall outlet in your home and at work provides a means to tap into electrical potential energy, waiting to turn a fan or drive a vacuum cleaner. A tightly coiled spring, a flexed muscle, and a stretched rubber band contain elastic potential energy, while a refrigerator magnet carries magnetic potential energy. In every case, energy is stored, ready to do work.
