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 4 s , his displacement relative to ground will be

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 4 s , his displacement relative to ground will be (A) 4.5 m (B) 5 m (C) 8 m (D) 3.2 m

Tardigrade Admin · Accepted Answer

Since, trolley is standing on frictionless surface, then it will move with velocity v. Applying law of conservation of momentum

80 \times 1 = (320 + 80) v

So,

v = 0.2 m / s

Then the relative velocity of the man with respect to earth

= 1 - 0.2 = 0.8 m / s

After 4 sec, the displacement relative to ground is given by

= 0.8 \times 4 = 3.2 m

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

4.5 m

5 m

8 m

3.2 m

Q. A man weighing $80 k g$ is standing on a trolley weighing $320 k g$ . 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 $4 s$ , his displacement relative to ground will be