1. Section 5-2

2.  The work done by a machine is work output. Work output = resistance force x resistance distance.  The work done on a machine is work input. Work input = effort force x effort distance.

3. Machines cannot increase the amount of work you do so the work output can never be greater than the work input.

4.  Not all work put into machines is useful work. Some of the work is used to overcome friction. This work is lost as heat energy. Efficiency = work output/work input x 100. Expressed as a percentage. Always less than 100% because work output is always less than work input.