Question 1080912
The braking distance D in feet required to stop a car traveling x miles per hour on dry, level pavement can be approximated by Upper D equals one sixteenth x squared: D = {{{1/16}}}x^2.
 (a) Calculate the braking distance for 30 miles per hour and 70 miles per hour. How do your answers compare?
D = {{{1/16}}}*30^2
D = {{{900/16}}}
D = 56.25 ft
&
D = {{{1/16}}}*70^2
D = {{{4900/16}}}
D =  326.67ft
:
(b) If the braking distance is 49 feet, estimate the speed of the car.
Estimate 27 mph
 (c) Use a calculator to solve part (b) numerically. Do your answers  agree? 
{{{1/16}}}x^2 = 49
x^2 = 49 * 16
x = {{{sqrt(784)}}}
x = 28 mph