# Mechanical energy

The total amount of kinetic and gravitational potential energy used to do a particular work is called mechanical energy. The energy of an object is said to be mechanical if it is in motion or changing its position. The potential energy stays 0 if an object is moving. The potential energy does not stay zero if the object is stationary. The equation that we use to calculate mechanical energy is ME = KE + PE. ME = ½mv^2 + mgh. M is the mass of the object. V is the velocity. G is the gravitational acceleration. H is the height where the object is.

A boy with a mass of 50kg is standing on top of a 50-meter building. What is the mechanical energy that the boy possesses?

- The kinetic energy is 0 as the boy is not in motion

ME = 0 + 50x10x50 = 25000 joules

A girl with a mass of 55kg is standing on top of a 52-meter building. What is the mechanical energy that the girl possesses?

- The kinetic energy is 0 as the girl is not in motion

ME = 0 + 55x10x52 = 28600 joules