A block `B` of mass `10 kg` is placed on smooth horizontal surface over it another block `A` of same mass is placed. `A` horizontal force `F` is applied on block `B`. `S_(1)` : No block will move unless `F gt 10 N`.
`S_(2)` : Block A will move towards left.
`S_(3)` : Acceleration of block B will never be less than that of `A`.
`S_(4)` : The relative motion between `A` and `B` will start when `F` exceeds `10 N`.

Options

A. `FFFF`
B. `TTTT`
C. FFTF
D. `TTFF`

Answer

C

Explanation

`mv(dv)/(dx)=ma-kx`
`underset(0)overset(0)intmvdv=underset(0)overset(x)int (ma-kx)dx`
`x=(2ma)/(k)`