When is mechanical energy not conserved

Sum of potential and kinetic energy

In physical sciences, mechanical energy is the sum of potential energy and kinetic energy.

The principle of conservation of mechanical energy states that if an isolatedsystem is subject only to conservative forces, then the mechanical energy is constant. If an object moves in the opposite direction of a conservative net force, the potential energy will increase; and if the speed (not the velocity) of the object changes, the kinetic energy of the object also changes.

In all real systems, however, nonconservative forces, such as frictional forces, will be present, but if they are of negligible magnitude, the mechanical energy changes little and its conservation is a useful approximation.

Conservation of mechanical energy worksheet

In elastic collisions, the kinetic energy is conserved, but in inelastic collisions some mechanical energy may be converted into thermal energy. The equivalence between lost mechanical energy and an increase in temperature was discovered by Jame's Prescott Joule.

Many devices are used to convert mechanical energy to or from other forms

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