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virtus
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A 6m high vertical street lamp stands on horizontal ground. A 2 metre tall man runs away from the street lamp at a constant speed of 2.5m/s. When he is y metres from the street lamp his shadow has length x metres.
Find the rate at which his shadow lengthens
 2 years ago
 2 years ago
virtus Group Title
A 6m high vertical street lamp stands on horizontal ground. A 2 metre tall man runs away from the street lamp at a constant speed of 2.5m/s. When he is y metres from the street lamp his shadow has length x metres. Find the rate at which his shadow lengthens
 2 years ago
 2 years ago

This Question is Closed

virtus Group TitleBest ResponseYou've already chosen the best response.0
dw:1342236117226:dw
 2 years ago

timo86m Group TitleBest ResponseYou've already chosen the best response.3
dw:1342236213718:dw
 2 years ago

virtus Group TitleBest ResponseYou've already chosen the best response.0
i don't understand?
 2 years ago

timo86m Group TitleBest ResponseYou've already chosen the best response.3
dw:1342236435888:dw
 2 years ago

timo86m Group TitleBest ResponseYou've already chosen the best response.3
dw:1342236535853:dw
 2 years ago

timo86m Group TitleBest ResponseYou've already chosen the best response.3
keep the light as the origin is 0
 2 years ago

timo86m Group TitleBest ResponseYou've already chosen the best response.3
and the ground as zero also
 2 years ago

timo86m Group TitleBest ResponseYou've already chosen the best response.3
there fore slope for the hypotonuse form is dy/dx (62) = dy which is fixed i think so 4 4/(02*x)
 2 years ago

timo86m Group TitleBest ResponseYou've already chosen the best response.3
dw:1342237451450:dw
 2 years ago

timo86m Group TitleBest ResponseYou've already chosen the best response.3
dw:1342237577634:dw
 2 years ago

timo86m Group TitleBest ResponseYou've already chosen the best response.3
sfx x = 3.75*x1 by x i mean x+y 3.75*x1=2.5x1+unkn unkn = 6.25*x1
 2 years ago

timo86m Group TitleBest ResponseYou've already chosen the best response.3
dw:1342238127714:dw another way to look at it
 2 years ago

timo86m Group TitleBest ResponseYou've already chosen the best response.3
where m1= (64)/(2.5x) and m2=  6/ (2.5x+b) set them equal to eachothter find b
 2 years ago

timo86m Group TitleBest ResponseYou've already chosen the best response.3
b=5x so s a b 1 2.5 5 2 5 10 3 7.5 15 It looks like everysecond the shadow gets 5 meters longer so it is a constant growth of 5 m/s i think
 2 years ago

robtobey Group TitleBest ResponseYou've already chosen the best response.0
From the figure,\[\frac{y+x}{6}=\frac{x}{2} \]The Total Derivative of the above equation is:\[\frac{1}{6} (dx+dy)=\frac{dx}{2} \]Solve for dx:\[dx=\frac{dy}{2} \]Replace dy with 2.5 and simplify.\[dx=1.25 m/\sec \]
 2 years ago
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