In Drawing $($a$),$ a bullet whose mass is mbmb $=0\mathrm{.}011$ kgkg and a speed of v$0$v$0=497\mathrm{.}0$ m$/$sm$/$s enters a wood block at rest whose mass is$$ mm $=0\mathrm{.}34$ kgkg $.$ The block is attached to a spring whose spring constant is kk $=770\mathrm{.}0$ N$/$MN$/$M $.$ The vertical green dashed line indicates the spring's natural length. In drawing $($b$)$ the bullet is embedded in the wood block. Find the common speed of the block $+$ bullet.

Note: this is a collision $--$ it's time for you to review on collisions. What physics principle to apply?