Lesson 8 of 8
Work and simple machines
Goal: Calculate work done and explain how a machine makes work easier.
Work is done when a force moves something. Energy is transferred, so work is measured in joules.
Work done = force × distance movedForce in newtons (N). Distance in metres (m), in the direction of the force. Work done in joules (J).
- A machine makes work easier. A lever, a ramp or a set of pulleys can let you use a smaller force.
- There is a price. The smaller force has to move through a bigger distance. Without friction, force × distance stays the same, so the machine does not save you any work.
- Wheels help in a different way. They cut down friction.
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Key words in this lesson
Lever A rigid bar that turns about a pivot
Work done The energy transferred when a force moves an object
Joule The unit of work and of energy
Machine Something that makes work easier, such as a lever or a ramp