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. `(3mg^(2)t^(2))/8`
B. `(mg^(2)t^(2))/8`
C. 0
D. `(-mg^(2)t^(2))/8`

Answer

A

Explanation

`W_(N)+W_(Mg)=DeltaKE`
`W_(N)=1/2m(g/2t)^(2)-(-mg.1/2g/2t^(2))=(mg^(2)t^(2))/8+(mg^(2)t^(2))/4=3/8mg^(2)t^(2)`