Work, Energy and Power

Work

The work done on an object by a constant force F is FΔxcosθ, where F is the magnitude of the force, Δx, the magnitude of the displacement and θ, the angle between the force and the displacement.

Work-Energy Theorem

The net work done on an object is equal to the change in the object's kinetic energy OR the work done on an object by a resultant/net force is equal to the change in the object's kinetic energy.

Conservative Force

A force for which the work done in moving an object between two points is independent of the path taken.  (Examples are gravitational force, the elastic force in a spring and electrostatic forces (coulomb forces).

Non-conservative Force

A force for which the work done in moving an object between two points depends on the path taken.  (Examples are frictional force, air resistance, tension in a chord, etc.)

Principle of Conservation of Mechanical Energy

The total mechanical energy (sum of gravitational potential energy and kinetic energy) in an isolated system remains constant.

Power

The rate at which work is done or energy is expended.