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## Homework Statement

Consider a 18 speed bicycle, 3 gears are rotating with the pedal and 6 gears are rotating with rear wheel. Consider that the ones rotating with pedal, have radii 10 cm, 7 cm and 5 cm and the other ones have radii 3 cm, 4 cm, 5 cm, 6 cm, 7 cm and 8 cm. Calculate the torque on rear wheel gear for each different case if you apply to the pedal a force of magnitude 343 N. The force is vertical to the pedal, and it has a length of 17 cm. Explain why a bike needs that much speed, i.e. 18 speed.

## Homework Equations

Equations about the torque and momentum

## The Attempt at a Solution

I couldn't do anything.Actually

**τ**=d

**L**/dt

I thought that

**Fxr**

here r

_{1}=F'xr_{2}here r

_{1}is the pedal radius**here r**_{2}is the rear wheel radiuscause torques must be same why

**d**

**τ**=**dt And**

**L**/**is equal to**

**L****rxp**which they are not chaning during the time.Theres no external force and radius is same.

Any ideas