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

Options

A. (a) `(4Mg)/(k)`
B. (b) `(2Mg)/(k)`
C. (c) `(Mg)/(k)`
D. (d) `(Mg)/(2k)`

Answer

B

Explanation

From work-energy theorem, `W_g+W_s=0`

`impliesMgx-1/2kx^2=0impliesx=(2mg)/(k)`