A wrench with a length of 42cm is being used to unscrew a 72cm bolt. If a torque of 18Nm is needed to overcome the friction keeping the bolt in place, what is the minimum torque that must be applied to the wrench to unscrew the bolt?

1 Answer
Aug 8, 2017

F43N

Explanation:

I assume the question is meant to ask what is the minimum force required to unscrew the bolt.

Torque is given by the equation:

τ=rFsinϕ

where F is the applied force, r is the distance from the pivot (axis of rotation) that the force is applied, and ϕ is the angle at which the force is applied.

We can rearrange the equation for torque to find F.

F=τrsinϕ

We are provided the following information:

r=42cm=0.42m

τ=18Nm

And it is implied that ϕ=90o since no angle—nor the necessary information to calculate one—is provided.

Note that I am not including the radius of the bolt in the measurement of the total radius because I am assuming that this is the radius of the body of the screw and not the head of the screw.

Therefore, we have:

F=18Nm0.42m

=42.86N

43N