At what minimum distance should the brakes be applied to avoid a collision with

Question

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

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

Use the values from PRACTICE IT to help you work this exercise. A police investigator measures straight skid marks 24.0 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?

Explanation / Answer

1. a = - f / m = - (7.96 x 10^3) / (1.20x 10^3)

a = -6.63 m/s^2

vf^2 - vi^2 = 2 a d

0^2 - 35^2 = 2(-6.63)(d)

d = 92.3 m .....Ans

(B) vf^2 - vi^2 =2 a d

v^2 - 35^2 = 2(-6.63)(30)

v = 28.76 m/s

-----------------------------

now d = 24 m

Applying vf^2 - vi^2 =2 a d

0^2 - v^2 = 2(-6.63)(24)

v = 17.8 m/s ......Ans

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