What is the work done by a spring force in a cyclic process?

If a long spring is stretched by $0.02\, m$,its potential energy is $U$. If the spring is stretched by $0.1\, m$,then its potential energy will be

$A$ $15\, g$ ball is shot from a spring gun whose spring has a force constant of $600\, N/m$. The spring is compressed by $3\, cm$. The greatest possible velocity of the ball for this compression is ............. $m/s$ $(g = 10\, m/s^2)$.

The potential energy of a certain spring when stretched through a distance $S$ is $10 \, J$. The amount of work (in $J$) that must be done on this spring to stretch it through an additional distance $S$ will be

One end of a spring of spring constant $80 \ Nm^{-1}$ and unstretched length of $30 \ cm$ is fixed at point $A$ and the other end of the spring is fitted with a smooth ring of mass $300 \ g$ as shown in the figure. The ring is allowed to slide on a horizontal rod fixed at a height of $40 \ cm$. Initially the spring makes an angle of $60^{\circ}$ with the vertical and the system of spring and ring is released from rest. The speed of the ring when the spring becomes vertical is . . . . . . $ms^{-1}$.

$A$ spring of spring constant $200 \, Nm^{-1}$ is initially stretched by $10 \, cm$ from the unstretched position. The work to be done to stretch the spring further by another $10 \, cm$ is (in $J$)