Police measure the lengths of skid marks to determine the initial speed of a vehicle before the brakes were applied. Many variables, such as the type of road surface and weather conditions, play an important role in determining the speed. The formula used to determine the initial speed is S = 5.5ˆšd ˆ™ f where S is the speed in miles per hour, D is the average length of the skid marks in feet, and f is a constant called the "drag factor." At a particular accident scene, assume it is known that the road surface has a drag factor of 0.7.

a. Write an equation that will determine the initial speed on this road as a function of the lengths of skid marks.
b. Sketch a graph of this function.
c. If the average length of the skid marks is 60 feet, estimate the initial speed of the car when the brakes were applied.
d. Solve your equation from 11a for D. What can you determine using this equation?
e. Graph your equation from 11d.What shape is it?
f. If you traveled on this road at a speed of 65 miles per hour and suddenly slammed on your brakes, how long would your skid marks be?