Question

Given in the figure are two blocks $A$ and $B$ of weight $20\,N$ and $100\,N$, respectively. These are being pressed against a wall by a force $F$ as shown in figure. If the coefficient of friction between the blocks is $0.1$ and between block $B$ and the wall is $0.15$, the frictional force applied by the wall in block $B$ is

• A. 100 N
• B. 120 N
• C. 80 N
• D. 150 N

Answer 1

Answer: (B)

120 N

Answer 2

Assume the system is in equilibrium.
Net gravitational force must be balanced by friction force from the wall.
Force of friction $=120 N$