# Play with Pulleys

The size and combination of pulleys determines how fast they (and things that are attached) will spin.

## How it works

Connect cassettes containing different sized pulleys to broadcast a song, or make a cartoon pelican fly.

## Things to try or ask around the exhibit

• Do the different sized pulleys turn each other at different speeds?
• What combination of pulley sizes make the pelican fly or the song play, faster or slower?

## Background

By connecting different pulley cassettes together, different spin ratios can be created.

In this exhibit, pulleys that are 40 mm, 80 mm and 120 mm in size are combined together in cassettes. A cassette that contains an 80 mm and a 40 mm pulley has a size ratio of 2:1. In the time it takes the large 80 mm pulley (and things attached) to spin once, the small 40 mm pulley (and things attached to it) will spin twice. Their size ration is 2: 1 but their spin ratio is 1:2.

## Finding the science in your world

Pulleys of different sizes are used to generate spinning motions in automatic washing machines and car engines (fan belts).