Question

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 0.2 while that between B and floor is 0.5 when a horizontal force F of 245 N is appied on the block B , the force of friction between A and B is:

Answer 1

As the block B, together with block A is laying on rough surface with u=0.5(u is not the initial velocity it is mu) it will be able to accelerate if the applied force is greater than u(mA+mB)g=0.5(10)(10)=50N.

Hence the force applied is only 25N .hence there will be no acceleration and frictional force between A & B will not arise .

force between A and B is zero