Asked by Lindsay

At the instant a traffic light turns green, a car starts moving with a constant acceleration a of 3.05 m/s^2. At the same time a truck, traveling with a constant speed of 10.15 m/s, overtakes and passes the car. How far beyond the traffic light will the car overtake the truck? What will be the speed of the car at that instant?

This problem really confuses me. Are there certain steps I need to take in order to get the right answer?
Answered by bobpursley
They both travel the same distance, in the same time.
Car:
d= 1/2 3.05 t^2
Truck
d= 10.15t
set these equal, and solve for time.
Answered by Lindsay
What exactly do you mean by "set them equal?"
Answered by manny
"Set them Equal"

1/2 3.05 t^2 = 10.15t
Answered by Lindsay
Ok, the time I got was 2.624 s.
Now what?
Answered by bobpursley
use that time to find the distance the car went, and its velocity.
Answered by Lindsay
Which equation am I using for distance?
Answered by bobpursley
d=1/2 a t^2, as above.
Answered by Lindsay
Right. I plug in "1/2 x 3.05 x (2.58^2") and come out with 10.15 m.
But that's obviously not correct.

I know I'm doing something wrong, but I'm just not sure what. I'm sorry...this just isn't making much sense yet.
Answered by bobpursley
1/2 3.05 * t^2= 10.15t
t^2= 2*10.15t/3.05 divide through by t,
t= 6.66seconds

d= 1/2 a t^2 or d= 10.15t
Answered by Lindsay
Ohhh ok I see my mistake!

Thanks for your patience. :)
Answered by nn
how u got the time
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