Finding the torque?

Question

A bicyclist of mass 70.0 kg puts all his mass on each downward-moving pedal as he pedals up a steep road. Take the diameter of the circle in which the pedals rotate to be 0.40 m, and determine the magnitude of the maximum torque he exerts about the rotation axis of the pedals.

I need some help with this torque problem. What equations do I need to use? Thanks!

Answer 1

Torque is the cross product of force and distance. In this case, it's just F d. The force is the weight of the biker (mg) and the distance is half the diameter of the circle (in this case, .20 m).

Answer 2

The maximum torque is: M = mgr = 70*9.8* 0.20 = 137.2 Nm