Question

A block of mass 20 kg is acted upon by a force F = 30 N at an angle 53° with the horizontal in downward direction as shown. The coefficient of friction between the block and the horizontal surface is 0.2. The friction force acting on the block by the ground is (g = 10 m/s²)

(A)  40.0 N

(B)  30.0 N

(C)  18.0 N

(D)  44.8 N 

Answer 1

Correct option (C) 18.0 N

Explanation:

Max. frictional force

 =  f_max = μN 

μ(mg + F sin 53°)

= 0.2 (20 x 10 + 30 x 4/5)

= 44.8 N

As applied horizontal force is Fcos53° 

= 18N < f_max , friction force will also be 18 N.