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

Given,

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

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