In an accident of the freeway, a sports car made skid marks 240m long on the pavement. The police estimated the braking acceleration of the car to be -8.82m/s^2

Question

In an accident of the freeway, a sports car made skid marks 240m long on the pavement. The police estimated the braking acceleration of the car to be -8.82m/s^2 given the road and weather conditions. if this is correct, what was the minimum speed (in m/s) of the sports car when the brakes were applied ?

Answer 1

Use the kinematic equation

 

v_f² - v_i² = 2ad

 

v_f = final speed = 0 (came to a full stop)

 

v_i = initial speed (what you want to solve for)

 

d = distance traveled while speed changed from v_i to v_f

d = 240 m

 

a = constant acceleration = -8.82 m/s²

 

0 - v_i² = 2ad

 

-v_i² = 2(-8.82)(240) m²/s²

 

v_i = √[2(8.82)(240)] m/s ≅ 65.1 m/s

 

v_i is the minimum speed.