Will gears let children pull a piano uphill with their bikes?

A group of 10 and 11 year olds explore the science behind gears as they attempt to pull a piano up a hill.

Children meet an Olympic hill-climb cycling champion to learn about the gears on a bike. They learn about why their bikes have 8 gears, the difference between high and low gears and when you use them. They experience that the lowest gear (gear 1) makes it easier to cycle but they go slower, whereas the highest gear (gear 8) makes it harder to cycle but they go faster. How gears work is explained using model gears, linked together in pairs on a board. By counting the number of teeth on different-sized gears, and counting the number of times each linked gear turns, they learn about gear ratios. They then carry out a simple experiment on their bikes, to demonstrate the distance travelled for one turn of the pedal in different gears. The bike with a high gear (high gear ratio) has a smaller gear wheel and moves further than the bike with a low gear (low gear ratio). The bike with the low gear is easier to pedal. Children now use their understanding of gears to decide which gear they will need to use to pull the piano uphill.

Teacher Notes

Key Stage 2:

Could be used very effectively to introduce the idea that some mechanisms, including gears, allow a smaller force to have a greater effect. This could be used to prompt discussion around their own experience of cycling with gears. They could explore other real-life examples of machines that use gears to make work easier eg. egg-whisks/food mixers, tin-openers, clock gears etc. Pupils could investigate gear ratios themselves, using sets of ‘cogs’ made out of bottle tops fixed to a board, with corrugated cardboard round them to form the teeth, and count the number of turns of each cog. The quantitative concept of gear ratios can be used to challenge the more able.

Key Stage 3:

Could be used very effectively to introduce the idea that simple machines give bigger force but at the expense of smaller movement (and vice versa): product of force and displacement unchanged. They could extend their understanding of bicycle gears by considering the combined effect of both front and rear gear wheels.

Students could explore other examples where gears are used in real life eg. simple examples such as egg-whisks/food mixers, tin-openers, clock gears and more complex examples such as car gearbox, rack-and-pinion gears in car steering etc. Students could be encouraged to consider gears as a type of lever or ‘force-magnifier’, identifying the fulcrum or turning point, the effort force and the load force, in different gear systems and calculating the total work done.

Curriculum Notes

This clip will be relevant for teaching primary science at Key Stage 2 or Second Level in Scotland or physics at Key Stage 3 or Third Level in Scotland.