Physics GCSE: Energy Calculations

Work done by unbalanced forces

Unfortunately there are very few situations where there is only one force doing work. So before you can calculate the work done you need to find the resultant force that is acting.

Here is an example of the type of thing you may be asked:

What amount of work must be done by the lift for it to reach the top?

Work done = force x distance

= 5200 N x 10 m

= 52 000 J or 52 kJ

Note: Some of this energy is used to overcome friction, so the energy is lost as heat energy to the surroundings. The rest is stored in the lift as gravitational potential energy, as the lift is now higher up than it was before.