An ideal spring with spring-constants bung from the celling and a block of mass M is attached to its lower end. The mass is released with the spring initially unstretched. Then the maximum extension in the spring is:

Options

A. `(4Mg)/(k)`
B. `(2Mg)/(k)`
C. `(Mg)/(k)`
D. `(Mg)/(2k)`

Answer

b

Explanation

From conservation of energy `Mgh=1/2kx^2`
`:. (2Mgh)/(k)=x^2` But h=x
or `x=(2Mg)/(k)`