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melbel

What is the rate of decay of awesome-10 which has a half-life of 650 days?

  • one year ago
  • one year ago

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  1. melbel
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    I can't figure out how to solve these rate of decay questions, so I just made up my own as a way to help me learn this. How would I solve this?

    • one year ago
  2. Spectrum
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    if it has a half life of 650 time units it means every 650 time units 1/2 of the samle dissapears.

    • one year ago
  3. melbel
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    Yep. :) How would I find the rate of decay, though?

    • one year ago
  4. Spectrum
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    halflife= -ln2/k that is the half life equation

    • one year ago
  5. melbel
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    I have a formula \[N=N _{0}e ^{kt}\] How/where would I plug everything in?

    • one year ago
  6. melbel
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    I'm not sure I understand @Spectrum

    • one year ago
  7. prettyboy20202
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    I know spectrum

    • one year ago
  8. prettyboy20202
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    i gave him all right answers

    • one year ago
  9. prettyboy20202
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    for his teset he did good to

    • one year ago
  10. ktnguyen1
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    I think they are asking for k you got N=1/2No t=650 so you plug all numbers in and find k

    • one year ago
  11. melbel
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    I mean, I don't understand what he meant. I'm having a lot of trouble with logarithms, so I'm not quick on my feet. :P

    • one year ago
  12. melbel
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    \[N=\frac{ 1 }{ 2 }N _{0}^{650k}\] Okay, so what do I do next?

    • one year ago
  13. melbel
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    Would I put some test number in for No? Like 100 or something?

    • one year ago
  14. ktnguyen1
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    no,|dw:1354966748637:dw| you plug 1/2No for Nthen you can simplify for No

    • one year ago
  15. ktnguyen1
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    |dw:1354967053153:dw|

    • one year ago
  16. mahmit2012
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    |dw:1354952485674:dw|

    • one year ago
  17. mahmit2012
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    |dw:1354952600983:dw|

    • one year ago
  18. mahmit2012
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    |dw:1354952743876:dw|

    • one year ago
  19. mahmit2012
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    |dw:1354953110349:dw|

    • one year ago
  20. mahmit2012
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    I think now it makes sense. Doesn't it?

    • one year ago
  21. mahmit2012
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    KIS means keep it simple.

    • one year ago
  22. Outkast3r09
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    Derp still need help understanding =/

    • one year ago
  23. Outkast3r09
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    The easiest way I believe is to derive it from calculus (if you've taken Diff EQ , you should know how to). Doing this you get an equation much like yours only N_0 is denoted c \[A=ce^{kt}\]

    • one year ago
  24. Outkast3r09
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    now we're given two values to find what c is you need to know that \[N(0)=N_0\] \[N_0=ce^0=c\] \[N=N_0e^{kt}\]

    • one year ago
  25. Outkast3r09
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    same as your equation now we know that after 650 days , we will have half of the original amount soo \[N(650 days)=.5N_0\] \[.5N_0=N_0e^{650k}\] solve for k, divide by \[N_0\]

    • one year ago
  26. Outkast3r09
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    \[\frac{.5N_0}{N_0}=e^{650k}\] the initial N's cancel so you get \[.5=e^{650k}\] to get rid of e take the ln of both sides \[ln(.5)=650k\] \[\frac{ln(.5)}{650}=k\]

    • one year ago
  27. Outkast3r09
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    your rate of decay is \[\frac{ln(.5)}{650}=k\] your equation will be \[N=N_0e^{\frac{ln(.5)t}{650}}\]

    • one year ago
  28. ktnguyen1
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    @Outkast3r09 : same thing I did. That is why I was confused with @mahmit2012 had done

    • one year ago
  29. Outkast3r09
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    \[\frac{dP}{dt}=kP\] \[\frac{dP}{dt}-kP=0\] \[e^{\int{kdt}}=e^{kt+c}=ce^{kt}\]

    • one year ago
  30. Outkast3r09
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    you integrate the left side you'll just get that and the right side will be P

    • one year ago
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