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

The potential energy of a long spring when stretched by $2 \ cm$ is $U$. If the spring is stretched by $8 \ cm$,the potential energy stored in it is:

When a spring is stretched by $2 \, cm$,it stores $100 \, J$ of energy. If it is stretched further by $2 \, cm$,the stored energy will be increased by ............. $J$.

Show that the law of conservation of mechanical energy is obeyed by pulling or compressing the block tied at the end of a spring.

$A$ block of mass $m$ is pushed against a spring with spring constant $k$ which is attached to a wall. The block slides on a frictionless table as shown in the figure. The natural length of the spring is $\ell_0$ and it is compressed to half of its natural length when the block is released. What will be the final velocity of the block?

Two springs have their force constants as $k_1$ and $k_2$ $(k_1 > k_2)$. When they are stretched by the same force $F$,which of the following statements is true regarding the work done?