Question

A man weighing 80 kg is standing on a trolley weighing 320 kg. The trolley is resting on frictionless horizontal rails. If the man starts walking on the trolley along the rails at speed 1 m/s then after 4s his displacement relative to the ground will be –

• A. 5 m
• B. 4.8 m
• C. 3.2 m
• D. 3.0 m

Answer 1

Answer: (C)

3.2 m

Answer 2

V = $\frac{mu}{M + m} = \frac{80 \times 1}{400} = \frac{1}{5}m/s$

S = $\left( 1–\frac{1}{5} \right)t = \frac{4}{5} \times 4 = \frac{16}{5}$m