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Equation of the line for a second order decay |
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| Jun26-12, 03:42 PM | #1 |
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Equation of the line for a second order decay
What is it?!! I have tried plotting dummy data showing y values halving as x values double and no simple type of equation results (ie exponential, power, polynomial etc) - is this true? I thought such a standard function would be a simple one!
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| Jun26-12, 03:46 PM | #2 |
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Yes, it is pretty simple. You are talking about a simple "inverse" proportion: y= C/x or xy= C. When x doubles, that is, x becomes 2x, y must halve in order that the product be constant: (2x)(y/2)= xy= C. If you want to think of that as a "power" it is [itex]y= Cx^{-1}[/itex]
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| Jun26-12, 03:49 PM | #3 |
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Mentor
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EDIT -- Oops, beaten out by Halls again! 
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| Jun26-12, 04:10 PM | #4 |
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Equation of the line for a second order decay
Sorry guys _ I meant that the x value interval doubles eg y = 100, 50, 25, 12.5; x = 0, 10, 30, 70 ie a second order decay where x represents elapsed time ie the half-life of the decay is doubling. Any ideas?
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| Jun26-12, 04:49 PM | #5 |
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y=1000/(x+10)
You can express both x and y as functions of powers of 2 (2^n where n=0,1,2,...). Eliminate 2^n to find y as function of x. |
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