Problema Solution
the stopping distance d 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 160 ft, how many feet will it take the same car to stop when it is traveling 120 mph?
Answer provided by our tutors
let
d = the stopping distance
r = the speed
d = k(r^2)
where k is the constant we need to fin
if know that if a car is traveling 60 mph the stopping distance is 160 ft that is
160 = k*60^2 divide both sides by 60^2
k = 160/(60*60)
k = 2/45
the formula for the distance is
d = (2/45)(r^2)
for r = 120 mph we have
d = (2/45)(120^2)
d = 640 ft
when the car is traveling with 120 mph it will need 640 ft to stop.