A block of mass M is attached to the lower end of a vertical spring. The spring is hung from a ceiling and has force constant value k. The mass is released from rest with the spring initially unstretched. The maximum extension produced in the length of the spring will be:

Options

(a) 2 Mg/k
(b) 4 Mg/k
(c) Mg/2k
(d) Mg/k

Correct Answer:

Mg/k

Explanation:

Restoring force, f’ = – kx. where x is the extension produced in the spring.
Weight of the mass acting downward = Mg.
In equilibrium kx = Mg, x= Mg / k