Pulleys

How does the exhibit work?

Sit down on a chair. Raise yourself up with the rope. Do the same for the other two chairs.

What is the science behind it?

The best way to lift yourself or someone else is to use pulleys. A pulley consists of a disk with a rope wound round it. Using a pulley is better than not using one at all, because you can pull instead of lifting. But you still have to be strong.

If you put pulleys under and next to one another and run the rope from one to the next, you spread the weight over more rope. Then you have to pull more rope down to get to the same height, but you need less muscle power. The more pulleys there are, the easier it becomes.

For example: To go 15 cm up on the stool with two yellow pulleys, you have to have pull twice as much rope down. But you have to pull twice as little. On the stool with four yellow pulleys, you have to pull four times as much rope down, but you have to pull four times as little. And now you know what happens with six pulleys.

Pulleys on a sailing boat

Adjusting the shape of the sails on a sailing boat takes a lot of strength. Fortunately there are pulleys that make it easier.

Pulleys in a crane

There are pulleys in a crane. They are needed to easily lift up heavy items like cars or windmill blades.