Questions where a collision is followed by or involves spring compression/extension, requiring combined use of momentum conservation and energy methods to find spring constant or compression.
The block of mass $M$ moving on the frictionless horizontal surface collides with a spring of spring constant K and compresses it by length L. The maximum momentum of the block after collision is (1) $\sqrt{\mathrm{MK}}\,\mathrm{L}$ (2) $\frac{\mathrm{KL}^2}{2\mathrm{M}}$ (3) zero (4) $\frac{ML^2}{\mathrm{K}}$