# Very basic physics problem

1. Apr 10, 2009

### AcecA

1. The problem statement, all variables and given/known data
A particle is moving along a straight line such that its acceleration is defined as a = (-2v) m/s^2, where v is in meters per second. If v = 20 m/s when s = 0 and t = 0, determine the particle's velocity as a function of position, and the distance the particle moves before it stops.

2. Relevant equations
Basic kinematics equations

3. The attempt at a solution
I tried using dt = dv/a and integrating that, and I got t = (ln20 - lnv)/2, then I tried substituting it into s = s0 + v0t + (1/2)at^2, and now I'm stuck. Any help would be appreciated. Thanks :)

2. Apr 10, 2009

### rock.freak667

Use the fact that

$$a= \frac{dv}{dt}=v \frac{dv}{ds}$$