Question

A block of mass m is kept on a platform which starts from rest with constant acceleration g/2 upward, as shown in fig. Work done by normal reaction on block in time t is :

Answer 1

A block of mass m is kept on a platform which starts from rest with constant acceleration. means, block is situated in non - inertial frame of reference. so, we have to apply pseudo force to make it in inertial frame reference.

so, normal reaction acts on block , F = mg + ma

= mg + mg/2 = 3mg/2 [ where a = g/2 ]

so, displacement during time t, is S

S = ut + 1/2 at²

S = 0 + 1/2 × g/2 t² = gt²/4

now, workdone = F.S

= 3mg/2 × gt²/4

= 3mg²t²/8

hence, workdone by the normal reaction on the block in time t is 3mg²t²/8

Answer 2

Answer:1/2M(g+a)^2T^2

Explanation:Do it yourself!!