# Homework Help: How fast was the ball moving when it left the pool table?

1. Dec 5, 2004

### Tabe

Okay, here is my problem: In a wild shot, Bo knocks a pool ball of mass of .85 kilograms offa 95-cm high pool table, and the ball hits the floor with a speed of 6.0 m/s. How fast was the ball moving when it left the pool table?
I don't want to know the answer, I just want to know how to solve the problem, but I have no clue where to start. If someone could just help me get the problem started, or in the right direction, I would really appreciate it. Thanks!

2. Dec 6, 2004

### futb0l

i used the conservation of mechanical energy theorem...

$$\frac{1}{2} (0.85)v^2 + (0.85)g(0.95) = \frac{1}{2} (0.85)(6)^2$$

...

$$v^2 + 2g(0.95) = 36$$

...

$$v^2 = 36 - 18.62$$

so...

$$v = 4.16893272$$

Well - if u find any mistakes - pls feel free to comment.

3. Dec 6, 2004

### Tabe

I saw that formula in my physics book, but I wasn't sure if it would apply to the problem because we haven't really gone over it yet.
But I'm going to use it to solve the problem, because it is a lot more than I had, and I will ask about it tomorrow.
Thanks!