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- Thread starter gina4930
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(x^2+12^2)^1/2+(y^2+12^2)^1/2=39

Can somewhere tell me if this is right and where to go from here?

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I like Serena

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You mentioned something about a figure?

I'm afraid it's too hard for me to deduce what you're doing without a figure.

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HallsofIvy

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That is the "static" formula. To get a "dynamic" formula, relating the rates of motion, differentiate both sides with respect to t, using the chain rule. Your final formula will involve both dx/dt and dy/dt. You are given one and asked to find the other.

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I like Serena

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Hey HoI!

That looks like a very plausible interpretation of the problem!

That looks like a very plausible interpretation of the problem!

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1/2(x^2+144)^-1/2*(2x*dx/dt) + 1/2(y^2+144)^-1/2*(2y*dy/dt)=0

then I substituted in x=-5 , dx/dt= -2.5 , and y= (533)^1/2

When I solved for dy/dt I got two totally different answers. The first time I got -1.08 and the second time I got -.04. According to my online assignment, neither of these are correct. Can anyone point out my mistake? Thanks!

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I like Serena

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Looking good...

But how did you get y=(533)^1/2?

But how did you get y=(533)^1/2?

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And after that I get dy/dt=-1.084 m/s.

Since the problem asks how fast cart B is moving toward Q, the answer should be 1.084 m/s.

Can it be that it should be without a minus sign?

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I like Serena

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Good!

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