Bicycle Parts That Turn the Wheel

In the picture

1. 1Pedal — your foot pushes down here, and the crank arm carries it around in a circle.
2. 2Chainring — the large toothed ring at the front that the crank turns.
3. 3Chain — the loop of steel links that carries the force from the front to the back.
4. 4Rear cog — the small toothed wheel that the chain pulls around.
5. 5Rear hub — the centre of the back wheel, which the cog turns along with it.

Examples

• Standing up on the pedals to climb a steep hill makes the chain pull harder on the rear cog.
• When the chain slips off the chainring, the pedals spin freely and the bike stays still.

Quiz: Bicycle Parts That Turn the Wheel (Age 12)

1. 1

   You push down on a pedal and the bike moves forward. Which path does the turning force actually take?

   • Pedal and crank → chainring → chain → rear cog → wheel
   • Pedal and crank → chain → chainring → rear cog → wheel
   • Pedal and crank → rear cog → chain → chainring → wheel
2. 2

   Halfway through a ride, the chain snaps. What happens if you keep pedalling?

   • The pedals lock up and will not move at all
   • The pedals still turn, but no force reaches the back wheel
   • The back wheel spins even faster because the chain is no longer holding it
3. 3

   The chain pulls the small rear cog around. How does that make the whole back wheel turn?

   • The cog presses against the tyre and rolls it forward
   • The cog tugs the spokes one by one to drag the wheel round
   • The cog is fixed to the hub at the centre of the wheel, so the wheel turns with it

The answers, each with its explanation, are in the app. This lesson has left the free week, so its quiz is part of the subscription.