# Homework Help: Acceleration vs Time Find Velocity

1. Sep 18, 2007

### circuscircus

1. The problem statement, all variables and given/known data
The graph shows acceleration versus time of a particle moving along the x axis. Its initial velocity is 8m/s at t=0. What is the particle's velopcity at t=4s?

http://img259.imageshack.us/img259/6684/graphcc9.jpg [Broken]

2. Relevant equations

3. The attempt at a solution

vi=8
ti=0
vf=??
tf=4

I was thinking of integrating y=-x+4 but I don't think I'm suppose to do that and also I don't know how to find +c.

Last edited by a moderator: May 3, 2017
2. Sep 18, 2007

### learningphysics

What does the area under an a-t graph represent?

3. Sep 19, 2007

### circuscircus

Well integrating the acceleration gets you velocity, does it not?

4. Sep 19, 2007

### robphy

You don't really want to integrate "y=-x+4"... with those variables.
When you integrate the function with the appropriate physical variables, what is the physical interpretation of your "c" constant of integration?

You don't need to actually do the integral [with calculus]... you can do it geometrically using learningphysics' suggestion.

Last edited: Sep 19, 2007
5. Sep 19, 2007

### circuscircus

Well the area under the chart is 8 at 4 seconds but that's the vi so how doe sthat come into play?

6. Sep 19, 2007

### robphy

Try your integration method, as well.