Part A If the coefficient of kinetic friction between tires and dry pavement is
ID: 1263914 • Letter: P
Question
Part A
If the coefficient of kinetic friction between tires and dry pavement is 0.800, what is the shortest distance in which an automobile can be stopped by locking the brakes when traveling at 29.8m/s ?
Express your answer using two significant figures.
Part B
On wet pavement the coefficient of kinetic friction may be only 0.250. How fast should you drive on wet pavement in order to be able to stop in the same distance as in part A? (Note: Locking the brakes is not the safest way to stop.)
Express your answer using two significant figures.
Explanation / Answer
The work done of the tires will be the change in KE of the car. Thus, as KEf = 0,
uk m g d = 1/2 m vi^2
--> d = [1/2 vi^2] / [uk g]
Thus,
d = 57 m [ANSWER]
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d = [1/2 vi^2] / [uk g]
--> vi = sqrt [2 uk g d]
Thus,
vi = 17 m/s [ANSWER]