The formula S= 30fd can be used to estimate the speed, s, in miles hour that a car is traveling when it goes into a skid, where f is the coefficient of

friction and d is the length of the skid marks in feet.

per

On a busy highway with a speed limit of 70 mi/h, a truck ahead of Verna jackknifes

across the road. Verna skids to a stop 10 ft short of the truck. Her skid marks

measure 260 ft. Was Verna speeding?

No; her speed was only 63 mi/h.

Yes: her speed was 73.9 mi/h.

Yes: her speed was 75.3 mi/h

No: her speed was 70 mi/h