Initially the spring is un deformed. Now the force `F` is applied to `B` as shown in the figure. When the displacement of `B` w.r.t. `A` is `x` towards right in some time then relative acceleration of `B` w.r.t. `A` at that moment is:

Options

A. `(F)/(2m)`
B. `(F-kx)/(m)`
C. `(F-2kx)/(m)`
D. none of these

Answer

C

Explanation

`F-kx=mb` and `kx=ma`
Hence `m(b-a)h=F-2kx` .