Draw the free body diagram of block and platform. As
M>>m,the acceleration of the platform,
a= can be taken as zero and hence its velocity remains constant as 4m/s. Acceleration of the block is,
ablock.ground=µg=2 towards right
Let velocity of block wrt ground at time t be v (towards right), then
v=2tSolve the question w.r.t platform frame of reference.
block.platform=2m/s2 (towards right)
block,platform=(2t−4)m/s (towards right)
Initial velocity of block wrt platform is 4 m/s towards left.
Let s be the required distance, then