Problem

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 force

F

of 25 N is applied on the block

B

, the force of friction between

A

and

B

is a. 3 N b. 4 N c. 2 N d. zero