Work Done and Energy Transfer

WORK is DONE on an object when it is MOVED through a distance by a particular force.

Calculating Work Done

The equation to calculate work done is:

where:

• W represents work done and is measured in Joules (J) or Newton-metres (Nm).
• F represents the force applied and is measured in Newtons (N).
• s represents the distance moved by the object in the direction of the force and is measured in Metres (m).

Units of Work

• One JOULE of work is done when a force of ONE NEWTON causes an object to move a distance of ONE METRE.
• Work done in joules can also be expressed in NEWTON-METRES (Nm). Both units are EQUIVALENT to each other.

Energy Transfer

When work is done, ENERGY is transferred from one form to another.

For example, the chemical energy in muscles is converted into kinetic energy when a person PUSHES an object.

Heat Energy from Work Done

If work is done against frictional forces, the KINETIC energy is often transformed into THERMAL ENERGY, which can cause a RISE IN THE TEMPERATURE of the object involved.

For example, when a car BRAKES, the KINETIC ENERGY of the car, is converted into THERMAL ENERGY in the brake pads, which causes the temperature of the brake pads to INCREASE.