Posted by karon on .
the stopping distance d of a car after the brakes are applied varies directly as the square of the speed r if a car travelling 80mph can stop in 360ft, how many feet will it take the same car to stop when it is travelling 70mph

algebra 
Reiny,
d ∝v^2
d = k v^2
for the given...
360 = k(80)^2
k = 360/6400
= 9/160
so if v = 70
d = (9/160)(4900) = 275.625 ft