Hi all, I have (what should be) a relative simple question regarding the use of Kinematic equations: The problem is stated as: A station wagon, initially traveling east at 30m/s, decelerates uniformly until coming to a complete stop at a traffic light. How far was the driver from the traffic light, if it took 15 seconds for the vehicle to come to rest after the driver applied the brakes? I know the answer is 225m...but the solutions used this equation to solve it: X-Xo = [ (Vo + V)/2 ]* t = [(30m/s + 0m/s)/2] *15s = 225m This makes sense, but why can't one use this equation to solve it: X- Xo = Vot + 1/2gt^2 = 30m/s*15s + 1/2*10m/s^2*(15s)^2 ?? HELP! Thanks!!!