# How to derive this equation

1. Sep 4, 2010

### zeion

1. The problem statement, all variables and given/known data

I wanted to know how this equation is derived. Thanks.

2. Relevant equations

$${v_{f}}^2 = {v_{i}}^2 + 2a\Delta d$$

3. The attempt at a solution

$$v_{f} - v_{i} = \frac {\Delta d a} {\Delta v}$$

2. Sep 4, 2010

### Fightfish

We have the two relations:
$$t=\frac{v-u}{t}$$
$$s=\frac{1}{2}(u+v)t$$

Substitute the first into the second and the deed is done.

3. Sep 4, 2010

### bp_psy

Start from:
1. v=vo+at
2. r=ro+vo*t+(at^2)/2
Find t from 1 and replace in 2, do all the algebra and you are done.