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Question 675653: A pebble is dropped into a calm pond, causing ripples in the form of concentric circles. The radius of the outer ripple is increasing at a constant rate of 1 ft per second. When the radius is 4ft, at what rate is the total area of distributed water changing?
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! A pebble is dropped into a calm pond, causing ripples in the form of concentric circles. The radius of the outer ripple is increasing at a constant rate of 1 ft per second. When the radius is 4ft, at what rate is the total area of distributed water changing?
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A = (pi)r^2
dA = 2(pi)r*dr
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If dr = 1, solve for dA when r = 4
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dA = 2(pi)4*1
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dA = 8(pi)sq ft per second
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Cheers,
Stan H.
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