# Physics

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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 - ,

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 - ,

What exactly do you mean by "set them equal?"

• Physics - ,

"Set them Equal"

1/2 3.05 t^2 = 10.15t

• Physics - ,

Ok, the time I got was 2.624 s.
Now what?

• Physics - ,

use that time to find the distance the car went, and its velocity.

• Physics - ,

Which equation am I using for distance?

• Physics - ,

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

• Physics - ,

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 - ,

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 - ,

Ohhh ok I see my mistake!

• Physics - ,

how u got the time