SOLUTION: A typical car's stopping distance on dry pavement "d" in feet can be approximated by the function d= 0.034s2(squared) + 0.56s - 17.11. Where "s" is the sp

Algebra.Com
Question 303155: A typical car's stopping distance on dry pavement "d" in feet can be approximated by the function

d= 0.034s2(squared) + 0.56s - 17.11. Where "s" is the speed in miles per hour, of the car before braking.


A. How fast is the car going if it requires 100 feet for the car to stop after the brakes are applied?
Answer by nerdybill(7384)   (Show Source): You can put this solution on YOUR website!
A typical car's stopping distance on dry pavement "d" in feet can be approximated by the function
d= 0.034s2(squared) + 0.56s - 17.11. Where "s" is the speed in miles per hour, of the car before braking.

A. How fast is the car going if it requires 100 feet for the car to stop after the brakes are applied?
.
Replace d with 100 and solve for s:
d= 0.034s^2 + 0.56s - 17.11
100= 0.034s^2 + 0.56s - 17.11
0= 0.034s^2 + 0.56s - 117.11
Solve using the quadratic formula. Doing so yields:
s = {51.0, -67.5}
Toss out the negative solution -- doesn't make sense.
so, the car was moving at 51 mph.
.
Details of quadratic formula:
.
Solved by pluggable solver: SOLVE quadratic equation with variable
Quadratic equation (in our case ) has the following solutons:



For these solutions to exist, the discriminant should not be a negative number.

First, we need to compute the discriminant : .

Discriminant d=16.24056 is greater than zero. That means that there are two solutions: .




Quadratic expression can be factored:

Again, the answer is: 51.0287914140646, -67.4993796493587. Here's your graph:
RELATED QUESTIONS

A car with good tire tread can stop in less distance than a car with poor tread. The... (answered by Alan3354)
The braking distance D in feet required to stop a car traveling x miles per hour on; dry, (answered by Boreal)
The formule D=0.054x^2+0.058x describes the distance in feet D that it takes to stop a... (answered by stanbon)
Can someone please help me with this problem? Thank you so much. The braking distance... (answered by stanbon)
The braking distance D in feet required to stop a car traveling x miles per hour... (answered by ankor@dixie-net.com)
the braking distance D in feet to stop a car traveling x miles per hour on dry, level... (answered by macston)
A car with good tire tread can stop in less distance than a car with poor tread. The... (answered by jorel1380)
the braking distance between D in feet required to stop a car traveling x miles per hour... (answered by macston)
On dry pavement a car's stopping distance varies directly as the square of its speed. A... (answered by josmiceli)