SOLUTION: The stopping distance of a car after the brakes have been applied varies directly with the square of the speed. If a car traveling at 60 mph can stop in 180 ft., what is the distan

Question 599502: The stopping distance of a car after the brakes have been applied varies directly with the square of the speed. If a car traveling at 60 mph can stop in 180 ft., what is the distance needed to stop the same car traveling at 72 mph?
Answer by nerdybill(7384) (Show Source): You can put this solution on YOUR website!
The stopping distance of a car after the brakes have been applied varies directly with the square of the speed. If a car traveling at 60 mph can stop in 180 ft., what is the distance needed to stop the same car traveling at 72 mph?
.
When you see "direct variation" think:
y = kx
where k is a constant.
.
We find that constant from: "If a car traveling at 60 mph can stop in 180 ft"
y = kx
180 = k(60)
180/60 = k
3 = k
.
Our general formula then is:
y = 3x
.
now, we can answer:
what is the distance needed to stop the same car traveling at 72 mph?
y = 3(72)
y = 216 feet
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