Mechanical energy facts
When a given amount of mechanical energy is transferred (such as when throwing a ball, lifting a box, crushing a soda can, or stirring a beverage) it is said that this amount of mechanical work has been done. Both mechanical energy and mechanical work are measured in the same units as energy in general. It is usually said that a component of a system has a certain amount of "mechanical energy" (i.e. it is a state function), whereas "mechanical work" describes the amount of mechanical energy a component has gained or lost.
The conservation of mechanical energy is a principle which states that under certain conditions, the total mechanical energy of a system is constant. This rule does not hold when mechanical energy is converted to other forms, such as chemical, nuclear, or electromagnetic. However, the principle of general conservation of energy is so far an unbroken rule of physics - as far as we know, energy cannot be created or destroyed, only changed in form.
An example of a mechanical system: A satellite is orbiting the Earth influenced only by the conservative gravitational force; its mechanical energy is therefore conserved. The satellite is accelerated towards the Earth with an acceleration perpendicular to the velocity. This acceleration is represented by a green acceleration vector and the velocity is represented by a red velocity vector. Though the velocity is constantly changed with the direction of the vector because of the acceleration vector, the speed of the satellite is not since the magnitude of the velocity vector remains unchanged.
Mechanical energy Facts for Kids. Kiddle Encyclopedia.