# Homework Help: 2 cars drag racing question

1. Oct 1, 2009

### i_heart_you

2 cars drag racing question....

1. The problem statement, all variables and given/known data
The first car has a constant velocity of 40 m/s and moves 10 m before the 2nd car starts moving. The second car speeds up with an acceleration of 3.6 m/s^2. What is the time and the displacesment before the 2 cars actually meet?

2. Relevant equations
V=d/t
d=V1t x (1/2) a t^2.. i think?

3. The attempt at a solution
I figured out the time it took for the first car to travel 40 m... which would be equal to initial t for the second car. Since I want to find when the two cars have an equal displacement i set their displacements equal and it didn't really work out cause i ended up with a negative time for some reason?
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Oct 1, 2009

### kuruman

Re: 2 cars drag racing question....

Hi i_heart_you, welcome to PF.

Start by writing two kinematics equations, one for each car, giving the displacement as a function of time. The first one you posted is inapplicable here because it works for constant velocity only and the second one is incorrect. Don't guess, look 'em up.

3. Oct 2, 2009

### i_heart_you

Re: 2 cars drag racing question....

thanks for your help... i finally figured it out
i just had to split up the displacements into initial and final and make the final displacements equal to each other....