A projectile of mass 20 g has an initial horizontal velocity of 100 m/s when it hits and stops in a wood block of mass 0.403 kg. The block is sitting on a horizontal frictionless surface and is attached to a massless spring, initially relaxed, with spring constant 148 N/m. What is the maximum compression of the spring? since momentum is conserved, i used the equation mv(initial) = mv (final), and found the final velocity of the block, as a result of the mass hitting it, is 4.963, but i'm not sure where to go from here? ..or am i heading the right direction ?