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

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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) About Me  (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