Q. Two identical blocks are connected by a light spring. The combination is suspended at rest from a string attached to the ceiling, as shown in the figure- $2.190$ below. The string breaks suddenly. Immediately after the string breaks :

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A

Acceleration of both the blocks would be $g$ downward

B

Acceleration of centre of mass of the combined block system would be $g$ downward

C

Acceleration of upper block would be $2 g$ downward

D

Acceleration of lower block would be $g$ upward

Solution:

As the system is in free fall centre of mass of system will fall at $g$ and on upper block net downward force is $2\, m g$ (own weight + spring force) hence its initial acceleration is $2 \,g$.

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