Mechanical Energy Transfers

Mechanical energy is the sum of the kinetic and potential energy of an object.
Kinetic energy is the energy of an object due to its motion. The formula to calculate it is 1/2 mv^2 where:
- m is the mass (in kilograms, kg)
- v is the speed (in metres per second, m/s)
Potential energy is the stored energy of an object due to its position in a force field, particularly a gravitational or electric field.

Work done is the transfer of energy when a force moves an object. Work done is equal to the force applied multiplied by the distance moved in the direction of the force.
The formula to calculate work done is W = Fd where:
- W is the work done (in joules, J)
- F is the force (in newtons, N)
- d is the distance (in metres, m)
Work done against the gravitational force is called gravitational potential energy (GPE). The formula to calculate it is GPE = mgh where:
- m is the mass (in kilograms, kg)
- g is the gravitational field strength (approx. 9.8 N/kg on earth)
- h is the height (in metres, m)
Elastic potential energy is the energy stored in an object when it is stretched, squashed or twisted.

The law of conservation of energy states that energy cannot be created or destroyed, only transferred from one form to another.
In mechanics, the original energy (input) is often transferred into useful energy and wasted energy.
Efficiency is a measure of how much of the total energy is transferred into useful energy. The formula to calculate it is Efficiency = (useful output energy / total input energy) x 100%.