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1. The problem statement, all variables and given/known data

At the instant the traffic light turns green, an automobile starts with a constant acceleration a of 2.1 m/s^2. At the same instant a truck is 10.2 m down the road and traveling with a constant speed of 8.5 m/s. (a) How far beyond the traffic signal will the automobile overtake the truck? (b) How fast will the automobile be traveling at that instant?

2. Relevant equations

3. The attempt at a solution

s(t) = 1/2 a * t^2 + v0 * t + s0

a = acceleration

v0 = initial speed

s0 = initial position

Being for the truck

a = 0 m/s^2

v0 = 8.5 m/s

s0 = 10.2 m

and being for the car

a = 2.1 m/s^2

v0 = 0 m/s

s0 = 0 m

the equation will be:

8.5 m/s * t + 10.2 m = (There is a 1/2 here right?) (1/2)2.1 m/s^2 * t^2

Solving this I get 9.156s which is apparently incorrect.

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# Homework Help: Constant Acceleration Automobile

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