Question

A man of mass $100 \,kg$. is standing on a platform of mass $200 \,kg$. Which is kept on a smooth ice surface. If the man starts moving on the platform with a speed $30 \,m/sec$ relative to the platform then calculate with what velocity relative to the ice the platform will recoil?

• A. 5 m/sec
• B. 10 m/sec
• C. 15 m/sec
• D. 20 m/sec

Answer 1

Answer: (B)

10 m/sec

Answer 2

The correct option is (B): 10 m/sec.
Then the man is moving wrt the ice in the opposite direction at (30-V) velocity. Recoil velocity V = 10 m/s in the opposite direction of movement of the man.
100 * (30-V) - 200 * V = 0
300 V = 3000
Velocity of the man wrt to ice = 20m/s
(Their relative velocity = 30 m/s)