Question

the braking distance D in feet required to stop a car traveling x miles per hour on dry , level pavement can be approximated by D=1/9x^2

Answer 1

We can find as follows
x D=x^2/9
speed braking distance
mph in feet
20 44.44
60 400.00

b) x^2/9=16
x^2=144
x=12 mph