1. The problem statement, all variables and given/known data Reaction time can be crucial in avoiding a car accident. You are driving at 75 km/h [N] when you notice a stalled vehicle 48.0m directly ahead of you. You apply the brakes, coming to a stop just in time to avoid a collision. Your brakes provided a constant acceleration of 4.8m/s^2 . What was your reaction time. Given: Vi = 75 km/h [N] --> 20.8 m/s d = 48 m a = -4.8 m/s^2 [N] Vf = 0 2. Relevant equations d = vi.t + 1.2.a.t^2 3. The attempt at a solution I tried using the quadratic formula by plugging in the neccesary numbers into d = Vi.t + 1/2.a.t^2. I plug in all the numbers and this is it 48 = 20.8.t - 2.4t^2 - 2.4t^2 + 20.8.t - 48 = 0 a = -2.4 b = 20.8 c = -48 Now just by calculating the discriminant, it turns out to be a negative value. b^2 - 4ac = 20.8^2 - 4(-2.4 x -48) = 432.64 - 460.8 =28.16 The answer is that the reaction took 0.13 s. I assumed that there were going to be 2 roots, the one being positive would be the right answer.