Question 395469
The stopping distance of a car after the brakes are applied varies directly as the square of the speed r. If a car traveling 60 mph can stop in 200 feet, how many feet will it take the same car to stop when it is traveling 40 mph? :
:
Use ratio, relationship of speed to stopping distance
{{{r^2/s}}}
:
let s = stopping distance at 40
{{{60^2/200}}} = {{{40^2/s}}}
{{{3600/200}}} = {{{1600/s}}}
cross multiply
3600s = 1600 * 200
3600s = 32000
s = {{{320000/3600}}}
s = 88.89 ft to stop at 40 mph
:
: