Cracking the SAT Physics Subject Test

Here’s How to Crack It

Each of the two forces produces a torque, but these torques oppose each other. The
torque of F 1 is counterclockwise, and the torque of F 2 is clockwise.

The net torque is the sum of all the torques. Counting a counterclockwise torque as
positive and a clockwise torque as negative, we have

τ 1 = +r 1 F 1 = +(0.12 m)(100 N) = +12 N·m

and

τ 2 = −r 2 F 2 = −(0.08 m)(80 N) = −6.4 N·m

so