A block `A` of mass `2 kg` rests on another block `B` of mass `8 kg` which rests on a horizontal floor. The coefficient of friction between `A` and `B` is `0.2` while that between `B` and floor is `0.5`.When a horizontal floor `F` of `25 N` is applied on the block `B` the force of friction between `A` and `B` is

Options

A. `3 N`
B. `4 N`
C. `2 N`
D. zero

Answer

D

Explanation

Maximum value of friction between `B` and ground
`= mu N = mu (m_(A) + m_(B)) g`
`= (0.5) (2 + 8) (10)= 50N`
Since applied force `F = 25 N` is les than `50 N`. Therefore system wil not move and force of friction between `A` and `B` is zero