Experiments: Simple Machines

A Single Moveable Pulley

Safety rules: Parent supervision Take care with scissors Materials you need are: 2 empty sewing thread reels 2 dowel rods string scissors weights

Suspend the two sewing reels (pulleys) from a horizontal support (e.g. a curtain rail) as in the diagram. Attach the weight to the movable pulley, and pull on the thread attached to the fixed pulley to lift it. Compare the effort of lifting with the actual weight.

You should find that the effort to lift the weight is much less than the weight itself.

Broomstick Pulleys

You will need 2 broomsticks, about 3 metres of rope and three people.

Tie one end of the rope to one end of a broomstick. Wrap the rope around the broomsticks which are about 30 centimetres apart as in the diagram. Ask two friends to stand and hold the broomsticks firmly. You pull the free end of the rope.

No matter how hard they try to pull the broomsticks apart, you will easily be able to pull the broomsticks together. They are acting as movable pulleys.