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

Explanation

Let `mu` be friction coefficent between A and B. A 12 N force of A is rquired for slipping so
`mu m_(A)g=12 implies mu =0.3`
maximum force `(F_(B))` applied on B so that A and B move together.
`F_(B)=(m_(A)+m_(B)) a`
where a `=mug implies F_(B)=(m_(a)+m_(B))mug=(4+5)(0.3)(10)=27N`