- #1

SherlockOhms

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## Homework Statement

A woman is riding a unicycle. The mass of the woman is: m(w)=66.0 kg,

the mass of the unicycle is: m(u)=5.40 kg, the diameter of the unicycle

wheel is: d = 55.0 cm, and the length of the unicycle crank is L =

11.0 cm

What is the maximum torque that the woman is able to

generate just by using her weight to push on the unicycle

pedal?

## Homework Equations

τ = r x F

## The Attempt at a Solution

So, the maximum force that she can exert on the unicycle is her weight i.e. her mass times g. To find the torque all you have to do is multiply the length of the crank by the weight. I'm just wondering though why this is correct. I mean her weight acts vertically downwards, directly above the centre of the unicycle wheel. By the cross product formula r x F = |r||F|Sin(θ). But isn't theta in this case 0? Implying that the torque is 0, which can't be correct. I may just be visualizing this incorrectly though. If someone could explain this it'd be great. I'll attach a diagram of what I'm visualizing. Thanks.