$A$ spring block system is placed on a rough horizontal floor. The block is pulled towards right to give spring an elongation less than $\frac{{2\mu mg}}{K}$ but more than $\frac{{\mu mg}}{K}$ and released. Which of the following laws/principles of physics can be applied on the spring block system

Whether the spring force is conservative or non-conservative ?

A spring of spring constant $ 5 \times 10^3$ $ N/m$  is stretched initially by $5\,cm$ from the unstretched position. Then the work required to stretch it further by another $5\,cm$ is .............. $\mathrm{N-m}$

A spring is compressed between two blocks of masses $m_1$ and $m_2$  placed on a horizontal frictionless surface as shown in the figure. When the blocks arc released, they have initial velocity of $v_1$ and $v_2$ as shown. The blocks travel distances $x_1$ and $x_2$ respectively before coming to rest. The ratio $\left( {\frac{{{x_1}}}{{{x_2}}}} \right)$ is

Two springs of spring constants $1500\, N/m$ and $3000\, N/m$ respectively are stretched with the same force. They will have potential energy in the ratio

A spring of force constant $k$ is cut in two parts at its one third length. When both the parts are stretched by same amount, the work done in the two parts, will be