In essence, levers are simple machines that make work easier by multiplying the force you are using.Teachers may want to demonstrate how different levers help us in different ways by opening bottles, undoing screws and pulling out nails etc.
A corkscrew with a bottle and cork is a good example, the bottle does not have to be full, just that the cork is firmly planted in the neck of the bottle. By getting pupils to pull the cork out with the corkscrew after trying to pull it out with just their hands, they can clearly see that the lever makes the task much easier.
For other examples, take blocks of soft wood around 15cm x 15cm x 15cm. On one, hammer in a large nail, leaving about one centimetre of the nail head exposed. A claw hammer can then be used to lever it out. With another, sink a large bolt and accompany with a spanner of the same size. Likewise a large screw and screwdriver can be used.
A few examples of each of the above gives each pupil a chance to try for themselves how the levers assist them in each task.
Levers can be categorised into three main groups:
Type 1 Levers (see Fig 1)
The fulcrum (pivot) is between the effort and the load. Examples include see saws and the claw of a hammer.
Type 2 Levers (see Fig 2)
The load is between the fulcrum (pivot) and the effort. Examples include wheelbarrows, staplers and bottle openers.
Type 3 Levers (see Fig 3)
The effort is between the fulcrum (pivot) and the load. An example is a fishing rod.