Energy, Work and Power

Energy

Energy is a scalar quantity that refers to the ability to do work.
Energy can exist in various forms such as potential, kinetic, thermal, electrical, chemical, nuclear, and so on.
Energy cannot be created or destroyed, but it can be transferred or changed from one form to another. This principle is known as the law of conservation of energy.

Potential energy is the energy that an object possesses due to its position relative to other objects or its stored energy. Gravitational and elastic potential energy are two common forms.
Kinetic energy is the energy an object possesses due to its motion, and it is dependent on both the mass and speed of the object.

Work is done when a force that is applied to an object moves that object. The work done on an object is equal to the force multiplied by the distance over which the force acts.
No work is done if the object does not move or if the force is perpendicular to the direction of movement.
Work is a scalar quantity and it can either be positive or negative. Positive work is done by a force when it acts in the same direction as the motion of the object. Negative work is done when the force acts in the opposite direction to the motion.

The work-energy theorem states that the work done on an object is equal to the change in its kinetic energy. This theorem underlines the relationship between work and kinetic energy, allowing problems involving mechanical energy to be solved more directly.

Power is the rate at which work is done or energy is transferred.
It can be calculated by dividing the total amount of work done or energy transferred by the time taken.
Power is a scalar quantity, which measures how much work can be done or energy transferred in a given amount of time.
Higher power means a greater amount of work or energy transfer per unit of time.

Power is given by the following formula: Power = Work / Time
Alternatively, it can also be calculated as the product of the force and the velocity of the object: Power = Force x Velocity
The SI unit of power is the watt (W), which is equal to one joule of work per second.

Efficiency represents how much of the input energy is usefully transferred or transformed. It is usually expressed as a percentage and can be given by the formula: Efficiency = (Useful energy output / Total energy input) x 100%
No real system is 100% efficient due to energy losses, mostly as waste heat.