Question

Two blocks, of masses M and 2M, are connected to a light spring of spring constant K that has one end fixed, as shown in figure. The horizontal surface and the pulley are friction less. The blocks are released from rest when the spring is non deformed. The string is light.

(A) Maximum extension in the spring is 4mg/k.

(B) Maximum kinetic energy of the system is 2M²g²/k

(C) Maximum energy stored in the spring is four times that of maximum kinetic energy of the system.

(D) When kinetic energy of the system is maximum, energy stored in the spring is 4M²g²/k

Answer 1

Correct option (A) (B) (C)   

Explanation:

Maximum extension will be at the moment when both masses stop momentarily after going down. Applying W-E theorem from starting to that instant.

System will have maximum KE when net force on the system becomes zero. Therefore