# Conservation of Energy problem.

1. Nov 23, 2009

### cyspope

1. The problem statement, all variables and given/known data
A 0.030-kg bullet is fired vertically at 200 m/s into a 0.15-kg baseball that is initially at rest. How high does the combined bullet and baseball rise after the collision, assuming the bullet embeds itself in the ball?

2. Relevant equations
m1v1 + m2v2 = (m1 + m2) v'

3. The attempt at a solution

0.030 kg * 200 m/s + 0.15 kg * 0 m/s = (0.030 kg + 0.15 kg) v' = 6 = 0.18 v'
v' = 33.333 m/s
$$\Delta$$p = m(vf-vo) = 0.18 kg (33.333 m/s) = 5.999 = 6 kg * m/s

Ok, this is what I did so far. Even though I know the velocity of the bullet + ball, I don't know how high it went up because I think I need to know the time or acceleration to find x, which is height.

2. Nov 23, 2009

### Delphi51

The acceleration is -9.81 m/s².

3. Nov 24, 2009

### cyspope

but I don't know the time.

4. Nov 25, 2009

### Redbelly98

Staff Emeritus
Take a look at the kinematic equations for constant acceleration. One of them will work here.