Torque EX 2

The diagram shows the gravitational force acting on the pendulum, the pivot (black dot) and the lever arm.

To solve this problem we first move the two vectors ${\vec {r}}$ and ${\vec {F}}_{G}$ so that they are placed "tail to tail", then we draw the x-axis parallel to the lever arm and we determine the angle between them:

Since we drew the vector of the force in the "fourth quadrant" we conclude that the direction of the torque is clockwise and therefore the torque is negative:

$\tau =-F_{G}r\sin {\theta }=-(2.5)(0.6)\sin {37^{\circ }}=0.9Nm$