Concept of Distance and time. (basic question but no answer)

[nabet94]

Homework Statement

Car P is 1km from finish line with a speed of 35ms-1 and a uniform acceleration of 2/5ms-2
Car Y is 1.2km from finish line going at 44ms-1 and a uniform accelr of 1/2ms-1
show that Y passes p 220m before the finish line.

Homework Equations

v2=u2+2as
s=vt-1/2at^2

The Attempt at a Solution

so the acceleration when they are both in the same position is 0. thus i can use s=vt-1/2at^2 for both and cancel them out. so it would be 220=(44)t-(1/2)(1/2)t^2 for Y and for P it would be 220=(35)t-1/2(2/5)t^2. but then i end up with 0=9t-(1/20)t^2. then what? after that I'm lost.

 

[mishek]

so the acceleration when they are both in the same position is 0.

How did you come up with this?

thus i can use s=vt-1/2at^2 for both and cancel them out. so it would be...

Why minus?

The problem states that you have to prove that car Y passes the car P 220 m before the finish line. What is the distance that each car has to pass in order to get to that position, i.e. 220 m before finish line?