Question
To stop a car, first you require a certain reaction time to begin braking. Then the car slows down at a constant rate. Suppose that the total distance moved by your car during these two phases is 56.7 m when its initial speed is 85.0 km/h, and 24.4 m when the initial speed is 52.8 km/h.
(a) What is your reaction time?
(b) What is the magnitude of the deceleration?
(a) What is your reaction time?
(b) What is the magnitude of the deceleration?
Answers
drwls
85.0 km/h = 23.61 m/s
52.8 km/h = 14.67 m/s
Total distance = reaction time distance + braking distance
= V*t + V^2/(2a)
Write two equations in two unknowns and solve for the two unknowns, a and t.
56.7 = 23.61 t - (23.61)^2/(2a)
24.4 = 14.67 t - (14.67)^2/(2a)
52.8 km/h = 14.67 m/s
Total distance = reaction time distance + braking distance
= V*t + V^2/(2a)
Write two equations in two unknowns and solve for the two unknowns, a and t.
56.7 = 23.61 t - (23.61)^2/(2a)
24.4 = 14.67 t - (14.67)^2/(2a)