Consider a car speed of 25 m/s. A child runs out into the roadway in front of the driver, and the driver takes 0.5 seconds to react to this need to suddenly stop. The brakes provide a constant deceleration rate of -10 m/s2. How far does the car travel before coming completely to rest?
reaction time distance ... 0.5 s * 25 m/s = 12.5 m
braking time ... 25 m/s / 10 m/s^2 = 2.5 s
... average velocity ... (25 m/s + 0 m/s) / 2 = 12.5 m/s
... distance = 2.5 s * 12.5 m/s = 31.25 m