A block A of mass 4 kg is placed on another block B of mass 5 kg and the block rests on a smooth horizontal table. For sliding the block A on B, a horizontal force of 12 N is required to be applied on it. The maximum horizontal force that can be applied on B so that both A and B move together and the acceleration produced by this force is

Options

A. 25 N, 5 `m//s^(2)`
B. 27 N, 3 `m//s^(2)`
C. 30 N, 8 `m//s^(2)`
D. cannot be calculated from the given data.

Answer

b

Explanation

`F_(K) = mu_(K)m_(1)g = 12, mu_(K) = 3//g`
`F = mu_(k) (m_(1) + m_(2)) g = (3//g) (4 + 5) g = 27` N
`a = F//(m_(1) + m_(2)) = 27//(4 + 5) = 3ms^(-2)`