Let
x = distance from light
s = length of shadow
Then
(x+s)/15 = s/6
s = 2/3 x
(a) ds/dt = 2/3 dx/dt = 2/3 * 5 = 10/3 ft/s
(b) 5 + 10/3 = 25/3 ft/s
a light is hung 15 feet above a straight horizontal path. If a man is 6 feet tall is walking away from the light at a rate of 5 feet/sec.
a) how fast is his shadow lengthening?
b) at what rate is the tip of the man's shadow moving?
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