(a) At what minimum distance should the brakes be applied to avoid a collision w

Question

(a) At what minimum distance should the brakes be applied to avoid a collision with the other vehicle?
__________ m

(b) If the distance between the vehicles is initially only 30.0 m, at what speed would the collision occur?
__________ m/s

Use the values from ABOVE to help you work this exercise. A police investigator measures straight skid marks 32.0 m long in an accident investigation. Assuming a friction force and car mass the same as in the problem above, what was the minimum speed of the car when the brakes locked?
(c) _______________ m/s

Explanation / Answer

Using work energy theorem,

Wnet = 0.5 x m x vf2 - 0.5 x m x vi2

- f dx = 0 - 0.5 x m x vi2

dx = (0.5 x 1050 x 352)/ 7920 = 81.20 m

B)

B) friction, f = m a

so a = 7920/1050 = 7.54 m/s2

use v2 = u2 + 2 a d

v2 = 352 + 2 x (-7.54) x 30

v = 27.79 m/s

C)use v2 = u2 + 2 a d

0 = u2 + (2 x -7.54 x 32)

u =21.97 m/s

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