2 cars drag racing question

[i_heart_you]

2 cars drag racing question...

Homework Statement

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?

Homework Equations

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

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?

 

[kuruman]

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.

 

[i_heart_you]

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...