i've spent an hour reading this problem over and over again, trying to plug into the formulas but only came out with 2 or more unknown variables. I've not a clue to where to start, please help me.(adsbygoogle = window.adsbygoogle || []).push({});

Here goes..

during the investigation of a traffic accident, police find skid marks 90m long. They determine the coefficient of friction between the car's tires and the roadway to be .5 for the prevailing condition. Estimate the speed of the car when the brakes were applied.

choices are:

a. 9.49 m/s

b. 21

c. 29.7

d. 42

Here's how far i got .

givens:

d=90m

coeff=.5

vf=0

vi?

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# Motion and friction

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