# 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?

Apr 30, 2018

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

${\tau}_{\text{bolt}} = r F$

$\implies {\tau}_{\text{bolt"/r = F approx 33.3"N}}$

Now, recall,

$\tau = r F \sin \theta$

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

$\implies {\tau}_{\text{min" = rF approx 5"N"*"m}}$

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