An ideal spring with spring constant k is hung from the ceiling 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

Explanation

Applying work energy theorem for motion from (a) to (c )
`W_(g)+W_("spring")=DeltaKE`
`Mgx_(m)-(1)/(2)kx_(m)^(2)=(1)/(2)M(0-0)=0`
`therefore` maximum extension, `x_(m)=(2Mg)/(k)`