Work Done in Physics

Understanding Work Done

Work done in physics relates to the amount of energy transferred when a force causes an object to move.
It’s important to remember that work is done when a force moves an object, not simply when a force is applied. If the object doesn’t move, no work is being done.
The direction of the force and movement matter. Any part of the force that does not act in the direction of the movement does not do work.

The work done can be calculated using the formula: Work Done = Force x Distance.
The unit of work done is the Joule (J). One joule is defined as the amount of work done when a one newton force moves an object one meter.
Force is measured in newtons (N) and distance is measured in meters (m).
If the force and the motion occur at an angle, the force is split into components parallel and perpendicular to the motion. Only the component of the force parallel to the motion does work, and is calculated as Force x Distance x cos (angle).

Work done on an object is equal to the energy transferred to or from the object.
If you do work on an object you transfer energy to it. The object might gain kinetic energy, gravitational potential energy, elastic potential energy, etc.
Conversely, if an object does work on its surroundings, then energy is transferred from the object to the surroundings.

Lifting a book off the floor involves doing work against the force of gravity.
In the case where an object falls, work is done by the force of gravity on the object.
Pushing a box across a rough floor involves doing work against the frictional force.

When work is done over a period of time, the rate at which that work is done is described as power.
Power (measured in watts) equals work done (J) divided by time taken (s). The formula for power is: Power = Work Done / Time.
Therefore, power is the amount of work done per unit time. A more powerful machine does more work in the same time.