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 travelling 30 mph can stop in 50 ft, how many feet will it take

Algebra ->  Equations -> 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 travelling 30 mph can stop in 50 ft, how many feet will it take      Log On


   

Question 464009: 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 30 mph can stop in 50 ft, how many feet will it take the same car to stop when it is travelling 20 mph?
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
The stopping distance d of a car after the brakes are applied varies directly as the square of the speed r.
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d = kr^2
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Solve for "k" using "a car travelling 30 mph can stop in 50 ft"
50 = k*30^2
k = 50/900
k = 0.0556
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Equation:
d = 0.0556*r^2
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How many feet will it take the same car to stop when it is travelling 20 mph?
d = 0.0556*20^2
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distance = 22.22 ft
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Cheers,
Stan H.
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