n the figure shown, the spring deflects by < to position A ( the equilibrium position) when a mass m is kept on it. During free vibration, the mass is at position B at some instant. The change in potential energy of the spring-mass system from position A to position B is

`1/2` kx2
`1/2` kx2 - mgx
`1/2` `(1 + delta)^2`
`1/2` kx2 + mgx