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eva12
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A boat is pulled into a dock by means of a rope attached to a pulley on the dock. The rope is attached to the front of the boat, which is 7 feet below the level of the pulley. If the rope is pulled through the pulley at a rate of 10 ft/min, at what rate will the boat be approaching the dock when 100 ft of rope is out?
 2 years ago
 2 years ago
eva12 Group Title
A boat is pulled into a dock by means of a rope attached to a pulley on the dock. The rope is attached to the front of the boat, which is 7 feet below the level of the pulley. If the rope is pulled through the pulley at a rate of 10 ft/min, at what rate will the boat be approaching the dock when 100 ft of rope is out?
 2 years ago
 2 years ago

This Question is Closed

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
dw:1350689236706:dw
 2 years ago

eva12 Group TitleBest ResponseYou've already chosen the best response.0
how do you get the answer or solve it?
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
You must find a way to relate rate of the pully rope to the rate of the boat using the right angle triangle
 2 years ago

eva12 Group TitleBest ResponseYou've already chosen the best response.0
i do not understand this problem or how to approach it to solve it
 2 years ago

eva12 Group TitleBest ResponseYou've already chosen the best response.0
can someone help me
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
dw:1350690450622:dw
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
you can express the triangle as 7^2 + x^2 =r^2
 2 years ago

eva12 Group TitleBest ResponseYou've already chosen the best response.0
then what will x be and would r will stand for rate rigth
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
\[\frac{ dr }{ dt } = 10ft/\min\]\[\frac{ dx }{ dt }_{r=100}\]
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
I'm just calling r the length of ROPE
 2 years ago

eva12 Group TitleBest ResponseYou've already chosen the best response.0
so the equation 7^2+x^2=r^2 will be dr/dt=2x+2r
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
when we differentiate 7^2 + x^2 =r^2, we will get: 49 + 2x* dx/dt = 2r* dr/dt
 2 years ago

eva12 Group TitleBest ResponseYou've already chosen the best response.0
then i pug in 100 for r and 10 for x in the equation
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
no, dr/dt = 10 ft/min.. we don't know what x is
 2 years ago

eva12 Group TitleBest ResponseYou've already chosen the best response.0
49 +2x=2(100)= will = x is 75.5
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
no, we don't solve for x as x is always changing. that is essentially what the question is asking.
 2 years ago

eva12 Group TitleBest ResponseYou've already chosen the best response.0
so then how do i approach then
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
okay... so here's what we do, we have to equations that will help us solve this problem, namely: 7^2 + x^2 =r^2 49 + 2x* dx/dt = 2r* dr/dt are you with me so far?
 2 years ago

eva12 Group TitleBest ResponseYou've already chosen the best response.0
do i solve for 1 equation then the 2 one
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
First lets deal with this equation: 49 + 2x* dx/dt = 2r* dr/dt what are we looking for, well the question asks, "at what rate will the boat be approaching the dock?" The rate at which the boat is approaching the dock is represented by dx/dt (the rate of change of x), so we need to re arrange this equation for dx/dt
 2 years ago

eva12 Group TitleBest ResponseYou've already chosen the best response.0
dx/dt=2r*dr/dt49/2x
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
good.. what do we know, we know what dr/dt is, and we know what that r=100 at the point of interest. but we don't know what x is at this given instance, so what we need to do is express x in terms of r in the other other equation: 7^2 + x^2 =r^2 x = sqrt(r^249) now substitute that into our change of rates equation, and we know that r =100, and dr/dt= 10: dx/dt = (2(100)*(10)49)/2(sqrt(100^249) = your answer
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
no, it shouldn't be that big
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
you must have typed it in wrong in your calculator
 2 years ago

baldymcgee6 Group TitleBest ResponseYou've already chosen the best response.1
you're very welcome
 2 years ago
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