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November 11th, 2012, 04:55 PM   #1
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A particle moving around a circle and a point

Problem says:

A particle is traveling around the cirlce x^2 + y^2 =25 where x and y are measured in inches. At the instant the particle is at the point (3,4), dx/dt = 7/sec. Find dy/dt at this time

???
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November 11th, 2012, 05:11 PM   #2
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Re: A particle moving around a circle and a point

Quote:
Originally Posted by mathkid
Problem says:

A particle is traveling around the cirlce x^2 + y^2 =25 where x and y are measured in inches. At the instant the particle is at the point (3,4), dx/dt = 7/sec. Find dy/dt at this time

???
You can solve this using implicit differentiation with respect to t ...





Divide out the constant 2, then plug in, there is only one unknown so you can solve for it.

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November 11th, 2012, 05:19 PM   #3
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Re: A particle moving around a circle and a point

wait do I take the dx or the dy over to the otherside of equation and then divide by 2?

please show me so I can use as a key for future problems
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November 11th, 2012, 05:23 PM   #4
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Re: A particle moving around a circle and a point

wait I think I c

so 2y dy/dy = -2x dx/dt

dy/dt = -x dx/dt

= dy/dt = -3 dx/dt

dy/dt = -3(7/sec)

dy/dt = -21 inches/ second



holy ***** sh** its a miracle
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November 11th, 2012, 05:35 PM   #5
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Re: A particle moving around a circle and a point

Did you confirm the answer in the back of the book?

You made a small error, let's see if you can find it.

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November 11th, 2012, 05:37 PM   #6
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Re: A particle moving around a circle and a point

no even problems not in back of book

I don't see the error tell me please
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November 11th, 2012, 05:43 PM   #7
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Re: A particle moving around a circle and a point

mathkid, your work is only 5 lines, please check your work. You made an error in line 1 which you corrected in line 2, but you made another error in line 2.

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November 11th, 2012, 06:04 PM   #8
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Re: A particle moving around a circle and a point

ok Agent and TY for staying on me I c it

2x dx/dt + 2y dy/dt = 0

2y dy/dt = -2x dx/dt

y dy/dt = -x dx/dt

dy/dt = -x/y dx/dt

dy/dt = (-3/4)(7/1)

dy/dt = -21/4

= -5.25 in/sec

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November 11th, 2012, 06:23 PM   #9
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Re: A particle moving around a circle and a point

Very good [color=#0000BF]mathkid[/color], i wouldn't be helping you learn if i simply handed all answers to you, I thought in this particular case you were capable of spotting your error if you took the time to go over your work. Spotting our own errors is a very important procedure when learning mathematics of any level.

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November 11th, 2012, 06:26 PM   #10
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Re: A particle moving around a circle and a point

TY

I PROMISE I AM TRYING GOING ON 6HRS NOW WITHOUT MUCH OF A BREAK
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