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 :

Options

A. `(5mg^2 t^2)/(32)`
B. `(mg^2 t^2)/(8)`
C. 0
D. `- (mg62 t^2)/(8)`

Answer

A

Explanation

`W_N + W_(Mg) = Delta KE , W_N = 1/2 m (g/4t)^2 - ( - mg 1/2 . g/4 t^2) = (mg^2 t^2)/(32) + (mg^2 t^2)/(32) + (mg^2 t^2)/(8) = 5/32 mg^2 t^2`