Gears allow a small force to have a greater effect.
You will need:
Print out: Gears to print
A4 card to make gears, scissors, glue, split pins, thick card to attach gears to e.g. cardboard box, sharp pencil and sticky tack to make holes.
To make the gears:
Print out the PDF. Stick this to the A4 card and cut out the gears.
Make a hole in the centre of each gear by putting it on top of your sticky tack and forcing the pencil through it.
Position the gears on top of the thick cardboard so that the teeth of one gear are interlocking with the next gear. Mark the position of the centre of each gear using the pencil. Make a hole using the pencil and sticky tack.
Attach the gears to the card using the split pins.
Make a gear chain to create a low gear for cycling up hills.
Make a gear chain to create a high gear for cycling down hills.
Which gear would you choose for cycling on the flat and why? Make this gear chain.