Question

the blue rod in the figure pivots around a yellow axle at the left end. forces are applied as shown. what will happen to the rod? a. it will rotate cw b. it will rotate ccw c. it is in static equilibrium

Explanation:

Step1: Calculate the torque for each force

Torque formula is $\tau = rF\sin\theta$. Assume $\theta = 90^{\circ}$ (perpendicular forces), so $\sin\theta = 1$.

• For the $100N$ force: $\tau_1=100\times2 = 200N\cdot m$ (clock - wise torque)
• For the $60N$ force: $\tau_2 = 60\times(2 + 1)=180N\cdot m$ (counter - clock wise torque)
• For the $40N$ force: $\tau_3=40\times0 = 0N\cdot m$ (since the distance from the pivot is $0$)

Step2: Compare the net torque

Net torque $\tau_{net}=\tau_1-\tau_2=200 - 180=20N\cdot m$ (clock - wise)

Answer:

A. It will rotate CW