Question

Two blocks of mass 8 kg and 4 kg are connected a heavy string Placed on rough horizontal Plane, The 4 kg block is Pulled with a constant force F. The co-efficient of friction between the blocks and the ground is 0.5, what is the value of F, So that the tension in the spring is constant throughout during the motion of the blocks ? (g=10 ms^–2) 

(A) 40 N 

(B) 60 N 

(C) 50 N 

(D) 30 N

Answer 1

Correct option: (B) 60 N

Explanation:

frictional force on block of 4 kg = μmg 

= (0.5 × 4 × 10) 

= 20N 

frictional force on block of 8 kg = (0.5 × 8 × 10) 

= 40 N. 

F = 20 + 40 = 60 N 

both bodies will move together and tension will be constant.