Posted by Lindsay on .
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?

Physics 
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. 
Physics 
Lindsay,
What exactly do you mean by "set them equal?"

Physics 
manny,
"Set them Equal"
1/2 3.05 t^2 = 10.15t 
Physics 
Lindsay,
Ok, the time I got was 2.624 s.
Now what? 
Physics 
bobpursley,
use that time to find the distance the car went, and its velocity.

Physics 
Lindsay,
Which equation am I using for distance?

Physics 
bobpursley,
d=1/2 a t^2, as above.

Physics 
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. 
Physics 
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 
Physics 
Lindsay,
Ohhh ok I see my mistake!
Thanks for your patience. :) 
Physics 
nn,
how u got the time