Physics · SYSTEMS OF PARTICLES AND ROTATIONAL MOTION

For a rigid body rotating about a fixed \( z \)-axis, why do internal forces between particles do zero net work during rotation?

1. A
   Because the distance between any pair of particles remains completely invariant in a perfectly rigid body
2. B
   Because the angular velocity is identical for all particles
3. C
   Because internal forces act only perpendicular to the axis of rotation
4. D
   Because the net torque due to internal forces about any axis is non-zero