Question

A wrench with a length of `15 cm` is being used to unscrew a `3 cm` bolt. If a torque of `1 Nm` 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?

Answer 1

Let's derive the force needed to unscrew the bolt,

`tau_"bolt" = rF`

`=> tau_"bolt"/r = F approx 33.3"N"`

Now, recall,

`tau = rFsintheta`

Let's assume `theta = 90°` in this case. Hence,

`=> tau_"min" = rF approx 5"N"*"m"`

is the minimum torque needed to unscrew the bolt with the torque wrench.