ROTATIONAL MOTION

Why can a single force not produce complete equilibrium in a rigid body?

• Because it is too weak
• Because it always produces torque about points not on its line of action
• Only in vacuum
• Only if it is zero

What distinguishes mechanical equilibrium for a rigid body from that of a particle?

• There is no difference
• A rigid body requires only torque balance
• A rigid body requires both force and torque balance, while a particle needs only force balance
• A particle requires torque balance

What is the role of the center of mass in rotational motion under a couple?

• It accelerates rapidly
• It stops rotating
• It remains stationary or moves uniformly while the body rotates about it
• It changes position randomly

Why does a compass needle experience a torque when not aligned with Earth's magnetic field?

• Because the needle is charged
• Because the field is weak
• Because the forces are unequal
• Because the forces on its poles form a couple due to separated lines of action

What is the net torque on a rod of length 2a when two equal and opposite perpendicular forces F act at its ends?

• Zero
• aF
• 2aF
• F/a