Question

Police investigators examining the scene of an accident involving two cars measure 79-meter long skidmarks of one of the cars which nearly came to a stop before colliding. The coefficient of kinetic friction between rubber and the pavement is about 0.82. Estimate the initial speed of that car assuming a level road.

Answer 1

Answer:

$v_i = 36.65 m/s$

Explanation:

As we know that friction force on the car during it applied brakes is given as

$F_f = -\mu mg$

so the deceleration of the car is given as

$a = -\mu g$

now we can use kinematics to find the initial speed of the car

$v_f^2 - v_i^2 = 2 a d$

so we will have

$0 - v_i^2 = 2(-\mu g)(d)$

now plug in all the data in it

$v_i^2 = 2(0.82)(9.81)(79)$

$v_i = 36.65 m/s$