help physics?

Question

You have been asked to design a "ballistic spring system" to measure the speed of bullets. A bullet of mass 2.90 g is fired into a block of mass 1.80 kg. The block, with the embedded bullet, then slides across a frictionless table and collides with a horizontal spring whose spring constant is k=32.0 N/m. The opposite end of the spring is anchored to a wall. What was the speed of the bullet if the spring's maximum compression is 14.4 cm?

Answer 1

First, the collision of the bullet and the block is inelastic, so conservation of momentum applies. I assume the block was not moving.

vp*2.9/1000=vb*(1.8+2.9/1000)

where vp is the speed of the bullet, and vb is the speed of the combined block and bullet
note that
vb=vp*(2.9/(1000*(1.8+2.9/1000))

vb=vp*0.00160852

since there is no friction, the collision with the spring is elastic, so conservation of energy applies

.5*(1.8+2.9/1000)*vb^2=
.5*32.0*.144^2

vb=.607m/s

vp=377 m/s

j

Answer 2

Use Hooks Law to determine the force needed to make such a contraction. Don't forget to add the mass of the block and the mass of the bullet (note: they are NOT in the same units).

Not going to give you the answer for the question though :P