# I really need help

1. Mar 27, 2008

### ital_dj

[SOLVED] I really need help

I understand the very simple questions and all, but when the book throws all these extra things at me, I get so lost. You might've remembered my earlier post (my first one), so I'm back with a bit more.

Code (Text):
If it takes a human cannonball 1.5s to exit a 1.6m long cannon, what is the average net force acting on the performer if his mass is 65kg?
I tried using a a=$$\frac{v_{2}-v_{1}}{t}$$ equation, but that wouldn't work. I also tried the d = v t equation, but that wouldn't work either. I'm assuming I still use Fnet = ma for this.

For you answers could you also tell me why that works? Thanks a lot

EDIT: Additionally, I just read the sticky, and if a mod feels that it should belong in the homework section, please feel free to move it; but it's not really homework, as I'm just studying for a test.

Last edited: Mar 27, 2008
2. Mar 27, 2008

### olgranpappy

use
$$x=\frac{1}{2}a t^2 + v_0 t + x_0$$

and F=ma

3. Mar 27, 2008

### ital_dj

I'm still having trouble putting the formula together. I filled in the t's with the 1.5, but I've never heard of v_0... I've heard of v_1 though. Additionally, how is there an x on both sides of the equation?

4. Mar 27, 2008

### olgranpappy

v_0 is the initial velocity, which is...

x_0 is the initial position, which is...

x is the final position, which is...

5. Mar 27, 2008

### ital_dj

Ok, I finally got it. You're equation helped a little, but I was still confused by it. The final equation was d = 1/2at^2

Thanks a lot for the effort... I really don't think I'm going to do well on this test