# Homework Help: Finding original speed / acceleration

1. Feb 6, 2006

### mrserv0n

Im new to this stuff so bear with me. I am really only looking for help as to what equation I use to find these answers.

A truck covers 40.0m in 8.50s while smoothly slowing down to a final speed of 2.80 m/s.

A. Find the trucks original speed.

B. Find the its acceleration.

2. Feb 6, 2006

### endeavor

try using solving for 2 variables, initial speed and acceleration, in 2 equations:
x = v0*t + 1/2 *a*t2
and
v2 = v02 + 2*a*x

3. Feb 6, 2006

### mrserv0n

Im confused as to which is number is my accelartion and which is my velocity

4. Feb 6, 2006

### endeavor

you know 3 variables, x = 40.0m, t = 8.50s, and v = 2.80m/s
you need to find v0, the initial speed, and a, the acceleration

use your knowledge of algebra to find these 2 variables in 2 equations

5. Sep 19, 2008

### 07triumphd675

Sorry to bring this post back from the dead -- but I'm doing this problem right now, and is V0 supposed to be 0? If I use formula VFinal: 2.80 m/s = V0 + AT (A being unknown at this point) and T being 8.5 seconds...

I'm left with a mad scramble of algebra where V0 = .33m-A

I'm constantly getting confused as to what to use when in these kinematics equations.

a(acceleration) = Vf-V0/T

a= 2.8m/s - V0 / 8.5 s

How would I go about plugging that in...that would still leave me with two variables none of which I seem to be able to solve for.

6. Sep 19, 2008

### 07triumphd675

Is Vo supposed to be 40 m/ 8.5 s to get 4.71 m/s initial velocity?