When a force moves an object, energy is transferred. The amount of energy transferred is called the work done. Work done is found by multiplying the force by the distance moved along the line of action of the force: work done = force × distance, or W = F × s.
Work done is measured in joules (J), force in newtons (N) and distance in metres (m). Only movement in the direction of the force counts. A force at right angles to the movement does no work on the object.
The energy transferred is equal to the work done. When you lift a box, your muscles do work and chemical energy is transferred to the gravitational potential energy store of the box. When you push a crate across a rough floor, work is done against friction and the energy is transferred to the thermal store of the crate and the floor. For example, a 50 N force that moves a crate 4 m does 200 J of work.