Work, force and distance

Work is done whenever a force moves something.

Everyday examples of work include walking up stairs, or lifting heavy objects. Whenever work is done, energy is transferred from one place to another. Both energy and work are measured in joules, J.

Calculating work done

W = F × d

• W is the work done in joules, J
• F is the force applied in newtons, N
• d is the distance moved in the direction of the force in metres, m

• In the diagram above, 10 N is applied to move the box 2 m.
• Work done = 10 × 2 = 20 J

Power

Power is a measure of how quickly work is being done and so how quickly energy is being transferred.

Calculating power

P = E ÷ t

• P is the power in watts, W
• E is the work done (or energy transferred) in joules, J
• t is the time taken in seconds, s.

• For example, an electric drill transfers 3000 J in 15 s. What is its power?
• Power = 3000 ÷ 15 = 200 W

Gravitational potential energy

On Earth we always have the force of gravity acting on us. When we are above the Earth’s surface we have potential energy. This is called gravitational potential energy. The amount of gravitational potential energy an object on Earth has depends on its:

• Mass
• Height above the ground

In the…