Question

A man of mass m is standing on a plank of equal mass m resting on a smooth horizontal surface. The man starts moving on the plank with speed u relative to the plank. The speed of the man relative to the ground is?

• A. $2u$
• B. $\frac{u}{2}$
• C. Zero
• D. $\frac{u}{4}$

Answer 1

The correct option is C Zero

Since the man is moving on the plank and the plank is resting on the ground and the relative velocity of plank with respect to ground is zero

Therefore all objects on the plank have relative velocity zero with respect to the ground.