1. Tardigrade
  2. Question
  3. Physics
  4. 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

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Q. 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

UPSEEUPSEE 2012

Solution:

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
$=0.8 \times 4=3.2\, m$