Potential energy: Encyclopedia II - Potential energy - Examples

Potential energy - Examples

A book on a table has greater gravitational potential energy than the same book on the floor. However the same book has less gravitational potential energy than if it were even higher. In raising the book from the floor to the table, work was done by someone which is now stored as potential energy. (This energy was provided by the chemical energy stored in food). The presence of this potential energy could be demonstrated by sliding the book off the table. The book would gain kinetic energy from its velocity until it reached the floor. The kinetic energy would then be converted into heat and sound by the impact.

In another example in Wales at Dinorwig there are two lakes, one higher than the other. At times when surplus electricity is not required (and so is cheap), water is pumped to the higher lake. At times of peak demand for electricity, the water flows through turbines and generates electricity once more (see also pumped storage). (The process is not completely efficient and much of the original energy from the surplus electricity is wasted by friction). In this example the potential energy is stored by doing work against the force of gravity.

The factors that affect the amount of gravitational potential energy that is created are: the mass of the object, the distance that it is raised and the gravitational field strength. Raising the same object to the same height on the Moon would require less energy than on earth because the force of gravity on the Moon's surface is less.

Adapted from the Wikipedia article "Examples", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki