A block the of mass `4kg` is placed on another block of mass `5kg` and the block `B` rests on a smooth horizontal table for sliding the block `A` on `B` a horizontal force `12N` is required to be applied force on it How much maximum horizontal force can be applied on 'B' s that both `A` and `B` move together? Also find out the accleration proudced by this force
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Explanation

Here , ` m_(1) = 4 kg , m_(2) = 5 kg . `
Force applied on A , f = 12 N ,
This must atleast be equal to force of kinetic friction applied on A bt B
` f = f_(k) = mu_(k) R = mu_(k) m_(1) g ` ltbr gt` 12 = f_(k) = mu_(k) xx 4 g :. mu_(k) = (12)/(4 g ) = (3)/(g ) `
As block B is on smooth surface , therefore to move A and B togrther , (maximum) force F required to be applied on B = frictional force applied on a by A
`F = (3)/(g) (4+ 5 ) g = 27 N`
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