Thread: Mechanics/moments problem.

Truly stuck on this question, and not sure where the angle should be situated in the first place?

'The pedal of a bicycle is 18cm long. When it is pushed downwards by a cyclist it experiences a force of 350N. Calculate the moment when the pedal is horizontal and then when it is 65 degrees below the horizontal.'

Any help would be greatly appreciated!

The moment is calculated using the cross product:



where is the force being applied and is the vector from the center of the crank to the pedal. For this problem you can calculate the cross product as simply the magnitude of F times the magnitude of R times the sine of the angle between them.