Question

A block of mass 0.1 kg is held against a wall applying a horizontal force of 5N on the block. If the coefficient of friction between the block and wall is 0.5, the magnitude of the frictional force acting on the block is  

(A) 2.5 N 

(B) 0.98 N 

(C) 4.9 N 

(D) 0.49 N

Answer 1

Correct answer is (A) 2.5 N

N = 5N

(f)_max = mN = (0. 5)(5) = 2. 5 N

For vertical equilibrium of the block

F = mg = 0.98 N < (f)_max

Answer 2

Correct answer is (A) 2.5 N