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January 30, 2015

January 30, 2015

Posted by **c** on Sunday, November 13, 2011 at 11:33pm.

- calculus -
**Steve**, Monday, November 14, 2011 at 9:30pmd = 1/2 at^2 = 16t^2

t = sqrt(d)/4

total time = falling time + echo time

4 = sqrt(d)/4 + d/1080

Let s = sqrt(d)

s^2 + 270s - 4320 = 0

s = 15.15

d = 229.52 ft

Check:

falling time = sqrt(229.52/16) = 3.7875

echo time = 229.52/1080 = 0.2125

total: 4 seconds

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