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**1. Homework Statement**

A bullet of mass 9 g moving with initial speed 300 m/s passes through a block of mass 4 kg, initially at rest on a frictionless, horizontal surface. The block is connected to a spring of force constant 904 N/m. If the block moves 2 cm to the right after the bullet passed through it, find the speed at which the bullet emerges from the block and the magnitude of the energy lost in the collision.

**2. Homework Equations**

Conservation of momentum.

**3. The Attempt at a Solution**

Well initial mometum is just (.009)(300), and it must equal (.009)(Vf)=(4)(Vblk)

to solve for the block velocity immediately after the bullet passes, I used Vf = sqrt(2ad). I said acceleration was (904)(.02)/(4)...(may be where I went wrong). I took that velocity and plugged it back into the original momentum equation and got velocity of the bullet to be 111 m/s, which was wrong.