The coefficient of friction between block `A` of mass `m_(1)=5kg` and block `B` of mass `m_(2)=10 kg ` is `mu_(2)=0.5` . There is no friction froce between block `B` and fixed horizontal surface. A force of `300N` acts on block `B` in horizontal direction and a horizontal force of magnitude `F` acts on block `A` as shown , both towards right. Initially there is no relative motion between the blocks. The minimum value of `F` such that relative motion starts between `A` and `B` is `:`

Options

A. `200N`
B. `187.5N`
C. `150N`
D. 0

Answer

D

Explanation

If `F=0`
Then assuming no relative motion acceleration of `A+B=(300)/(15)=20m//s^(2)`
`:' 20m//s^(2)gtmug`
Where `mu+0.5 ` and `g=10m/s^(2)`
`:. ` relative motion shall exist. Hence `F=0N`.
`F=0`