Q.
Block $A$ of mass 2 kg is placed over a block $B$ of mass 8 kg. The combination is placed on a rough horizontal surface. If $g = 10ms^{- 2}$, coefficient of friction between $B$ and floor =0.5, coefficient of friction between $A$ and $B$ = 0.4 and a horizontal force of 10 N is applied on 8 kg block, then the force of friction between $A$ and $B$ is
A) 100 N
B) 50 N
C) 40 N
D) None of these
Explanation
(b) $f = \mu R = \mu mg\left| m\ \right.\ $is mass of the combination
$f = 0.5 \times 10 \times 10$ N = 50 N
So, a force of 10 N is unable to start the motion of the system. There is no relative motion between $A$ and $B$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.