Education Combining errors!

Discussion in 'General' started by Bogomip, 18 Nov 2008.

  1. Bogomip

    Bogomip ... Yo Momma

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    I was wondering if I could possibly get a bit of help combining errors. I have a few things I need to calculate the error for, and dont quite understand what im meant to do with some of them. They are all orbital elements.

    So what I know is the error in the distance between 2 planets, lets call this ed.

    I need help understand...

    Semi Major Axis
    The equation for this is...

    SMA = 0.5 ( distance2 - distance1 )

    where both distances have error ed shown above. The combinational error I came up with was...

    dSMA = (1 / sqrt(2)) * ed[/d]

    which in itself im not massively confident about :S



    The other things I need to find errors for are...

    eccentricity = ( distance2 - distance1 ) / ( distance2 + distance1 )

    where distance2 and distance1 again have error ed.

    Period = constant * SMA^3

    where the SMA = 0.5 ( distance2 - distance1 )

    Basically I just cant work out from my notes how I am meant to be combining some of this stuff :S There are more but tbh once I can work out the ones above I can get the others quite easily.

    Thanks for anything! :)
     
    Bogomip, 18 Nov 2008
    #1
  2. dragontail

    dragontail 5bet Bluffer

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    Scratch that. Don't trust a chemist on errors. Look below \/
     
    Last edited: 18 Nov 2008
    dragontail, 18 Nov 2008
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  3. Krikkit

    Krikkit All glory to the hypnotoad! Super Moderator

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    Had a look at my own notes on errors and managed to flesh this out for you mate. Hope it helps! :thumb:

    p.s. Anyone spots any mistakes, feel free to correct/berate me, I'm not massively good at errors myself. :(

    [edit]Bloody pdfhost... right load of rubbish!
    [edit2]Just noticed a mistake, right at the top, distance 2 = some value +/- sigma, not 2! :\
     
    Last edited: 18 Nov 2008
    Krikkit, 18 Nov 2008
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  4. Bogomip

    Bogomip ... Yo Momma

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    Thanks krikket :)

    Im shocking at errors, half the reason I changed to computational physics, not nearly as many errors to worry about :D Computers do things so much better than someone (me) in a lab!

    edit: does make me feel good about getting the SMA right though \o/ :D
     
    Bogomip, 18 Nov 2008
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  5. crazyg1zm0

    crazyg1zm0 Minimodder

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    what course is that?

    if it is chem what year as i aint done that sorta thing yet in my uni course tho have only just really started 2nd year so meah. tho if i should have donw it oh bugger i need to go over my notes
     
    crazyg1zm0, 19 Nov 2008
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  6. Krikkit

    Krikkit All glory to the hypnotoad! Super Moderator

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    Physics. The one thing they absolutely go sick for in a Physics degree is error analysis, and it makes me a very sad panda... :(
     
    Krikkit, 19 Nov 2008
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  7. Bogomip

    Bogomip ... Yo Momma

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    Computational Physics ;)

    Error makes me sad too, but since this is the first I have needed to do since second year it isnt too bad :D
     
    Bogomip, 19 Nov 2008
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