# The Difference Between Equation Uniform Acceleration and Average elocity

1. Aug 27, 2012

### Arooj

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

I was just wondering in what instances you would use the two equation belows, and what the difference is between them.

2. Relevant equations

average velocity:

vave = Δx/Δt

Uniform Acceleration:

vave = (vi+ vf )/2

3. The attempt at a solution
I'm assuming that the second equation is just a way of finding the average velocity of time and distance are not known.

2. Aug 27, 2012

### kushan

vave?

3. Aug 27, 2012

### SammyS

Staff Emeritus
The first equation, $\displaystyle v_\text{ave}=\frac{\Delta x}{\Delta t}$ is a definition for average velocity, so it's always true.

The second equation, $\displaystyle v_\text{ave}=\frac{v_\text{initial}+v_\text{final}}{2}$ is true for the case of uniform (constant) acceleration. It's not true in general, if the acceleration is not constant.