A boy and a block, both of same mass, are suspended at the same
horizontal level, from each end of a light string that moves over a
frictionless pulley as shown. The boy starts moving upwards with
an acceleration 2.5 m/s2 relative to the rope. If the block is to travel
a total distance 10 m before reaching at the pulley, the time taken
by the block in doing so is equal to :
Physics tutor for IIT JEE with more than 15 years experience and having produced ranks 26, 83, 133, 198, 298, 483 and many more.....
Make free body diagrams of the boy and block. Acceleration of the block would be same as that of boy because of same mass. Then using second equation of s = ut + 1/2 at t^2, you can find time taken by the block to cover the given distance.