Question

Two blocks of masses m₁ and m₂ are connected with a mass less unstretched spring and placed over a plank moving with an acceleration ‘a’ as shown in figure. The coefficient of friction between the blocks and platform is μ.

(A) spring will be stretched if a > μg

(B) spring will be compressed if a ≤ μg

(C) spring will neither be compressed nor be stretched for a ≤ μg

(D) spring will be in its natural length under all conditions

Answer 1

Correct option (D)

Explanation:

Let the value of ‘a’ be increased from zero. 

As long as a ≤ μg, there shall be no relative motion between m₁ or m₂ and platform, that is, m₁ and m₂ shall move with acceleration a. 

As a > μg the acceleration of m₁ and m₂ shall become μg each.

Hence at all instants the velocity of m₁ and m₂ shall be same 

The spring shall always remain in natural length.