To stop a car, first you require a certain reaction time to begin braking; then the car slows under the constant braking deceleration. suppose that the total distance moved by your car during these two phases is 56.9 m when its initial speed is 80.0 km/h, and 25.7 m when its initial speed is 50.7 km/h. what are (a) your reaction time and (b) the magnitude of the deceleration?

a)

b) a = 5.59 m/s²

Explanation:

given,

total distance traveled by the car to stop is 56.9 m when speed of vehicle is 80 km/h or 80 × 0.278 = 22.24 m/s

total distance traveled by the car to stop is 25.7 m when speed of vehicle is 50.7 km/h or 50.7 × 0.278 = 14.09 m/s

using stopping distance formula

................(1)

..............(2)

on solving both the equation we get

a = 5.59 m/s²

now reaction time calculation