Conversation of Energy

3. Potential Energy

Potential energy is differentiated from kinetic energy by the fact that it is the "stored" energy of an object at rest, although, just like kinetic energy, certain amounts of potential energy can be in an object in motion. There are two types of potential energy that we are concerned with, gravitational potential energy and spring potential energy.

Gravitational potential energy is the potential energy "created" by an object being higher or lower than some fixed "zero" point due to the force of gravity. It is given as mass times acceleration due to gravity times the height of the object from the fixed point.

The other type of potential energy is spring, also known as elastic, potential energy. This is potential energy pent up in a compressed spring, or spring-like mechanism, before it is released. Spring potential energy is one-half times the spring constant times the length compressed (or stretched) from the spring's normal length.

A brief discussion of the spring constant is in order. The spring constant is a measure of the overall "tension" (it's not technically tension, actually; tension is a type of force) or "springiness" of a spring. It is measured in kilograms ÷ seconds˛, or kg ÷ (s˛).

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