# Physics--Please Help!!

posted by
**Rob**
.

A bullet of mass m=0.060 kg hits a 5.0 kg block with an initial speed of 225 m/s. The block is connected to a spring that is attached to a wall. The friction between the block and the table is negligible. Upon impact, the bullet bounces back from the box with a speed of 75 m/s.

A) Calculate the speed of the block right after the collision.

I thought the equation to use was mv of bullet = (M+m)V of block. I came up with 2.67 but the answer is supposed to be 3.6 m/s.

B) As a result of the collision, the spring compresses to a mazimum of 0.20m. Find the spring constant

--The equation to this is 1/2mv^2 = 1/2kx^2 right? I can't get the answer to this question without the answer to part A.

C) Find the inelastic energy loss during the collision