finding distanced traveled

Question

The braking distance d, in feet, of a car traveling at speeds, in miles per hour, is modeled by the quadratic function d(s) = 0.05s2 + s. Find the braking distance of a car traveling on a highway at 75 mph. If a car required 150 feet to come to a stop, how fast was it traveling when its brakes were applied?

Answer 1

To find the breaking distance at 75 mph, evaluate   d(75).

 

 

To find the speed in which the brakes were applied from 150 feet, set d(s)=150 and solve for s.

 

150 = 0.05s² + s

 

0 = 0.05s² + s - 150

 

 

Use the quadratic formula to solve for s.