(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Kathy has a sports car that can accelerate at the rate of 4.90m/s^2. She races with Stan. Both cars start from rest but experienced Stan leaves starting line 1.00s before her.

Stan moves with a constant aceleration of 3.90m/s^2 and Kathy maintains an acceleration of 4.90m/s^2

a) find time at which Kathy overtakes Stan

b) The distance she travels before she catches him

c) speed of both cars the instant she overtakes him

2. Relevant equations

Position as a function of time: xf= xi + vxi*t + 1/2*ax*t^2

velocity as a function of time: vxf= vxi + axt

3. The attempt at a solution

Well there was a similar example in the book but it involved a trooper and it started at vi=0 and chased a car with constant acceleration. The car was at a constant v and the trooper started chasing it after 1s after it passed a bilboard where the trooper was stationed. The thing is they gave the velocity and and since you knew that since it was 45.0m/s then after 1 s the initial distance of the car from the billboard was 45.0m and that was when the trooper started to move.

For this question I'm given acelleration for both. This has gotten me a bit confused as to how to go about finding the displacement of the cars and also since the initial v for both cars is 0.

Kathy

vi= 0m/s

a= 4.90m/s^2

Stan

vi= 0m/s

a= 3.50m/s^2

I don't know if it is correct but ...

-don't I need to find the position of Stan when Kathy starts to drive?

I don't know how to find that though.

For position as a function of time

xf= xi + vxi*t + 1/2 ax* t^2

xf Kathy= 0 + 0 + 1/2 (4.90m/s^2)(t^2)

xf Kathy= 1/2(4.90m/s^2)*(t^2)

Would it be the same for Stan? like this:

however stan starts 1.00 sec ahead of her...HOw do I visualize what I need for the problem?

I know I need the distance x which equates to both but how I include the 1.00 s is kind of confusing.

Is the time negative or positive? The book ex of the other one had a diagram like this:

t= -1.00s ------------t= 0s------------t= ?s

xf= xi + vxi*t + 1/2 ax* t^2

xf Stan= 0+ 0t + 1/2( 3.50m/s^2)(t^2)

Would I equate these 2 equations?? I'm trying to figure out how I incorperate the 1.00s since right now it is like they both started at the same time if I'm not incorrect.

HELP!

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# Homework Help: When will Kathy overtake Stan if he starts 1.00s before her with constant a

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