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. 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 on block B is 

(A) 80 N 

(B) 120 N 

(C) 150 N 

(D) 100 N

Answer 1

Correct option is (B) 120 N

Normal force on block A due to B and between B and wall will be F.

Friction on A due to B = 20 N

∴ Friction on B due to wall = 100 + 20 = 120 N

Answer 2

correct answer is (B) 120 N