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EMERGENCY HELP NEEDED PLZZ

Discussion in 'International A And AS Level' started by MysteRyGiRl, May 30, 2011.

  1. MysteRyGiRl

    MysteRyGiRl

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    heyy can sm1 plz help me out wd AS physx uncertainity question? given below
    The density of the material of a rectangular block is determined by measuring the mass and
    linear dimensions of the block. The table shows the results obtained, together with their
    uncertainties.
    mass = (25.0 ± 0.1) g
    length = (5.00 ± 0.01) cm
    breadth = (2.00 ± 0.01) cm
    height = (1.00 ± 0.01) cm
    The density is calculated to be 2.50 g cm–3.
    What is the uncertainty in this result?
    i hv board papers nxt ...2 nxt week n i wd rely appreciate sm1s help thank u :)
     
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  3. MysteRyGiRl

    MysteRyGiRl

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    ummmm 1 more question plzz
    A quantity x is to be determined from the equation
    x = P – Q.
    P is measured as 1.27 ± 0.02 m.
    Q is measured as 0.83 ± 0.01 m.
    What is the percentage uncertainty in x to one significant figure?
     
  4. Apoclaypse

    Apoclaypse

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    when solving these u have to rember one thing ,, uncertainnities are always added.! right mate!

    ok on question now,, density =mass/volume,, so find v first and error in we.
    V= length x width x height. 2*5*1= 10
    V=10 uncertainity would be

    x/10=.01/2 + .01/5 +.01/1 by solving this we get x=.17 now put this into d=m/v

    x/2.5=.1/25+.17/10 uncertainty in density is .05
     
  5. MysteRyGiRl

    MysteRyGiRl

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    thank u soooooooo much :D
    cd u plz answer da scnd 1 too?
     
  6. Apoclaypse

    Apoclaypse

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    Subtract p from q and add their uncertainity!! 1.27-.83=.44 .01+.02=.03
    x=.44±.03
     
  7. Apoclaypse

    Apoclaypse

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    there u go!
     
  8. thunderingthunder

    thunderingthunder

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    ATC:x=P-Q..
    So....x=1.27-0.83=0.44....
    %age uncertainty is (error in x/x)x100....we dont have error in x..we will calculate it...lyk this:
    error in x/x=error in P/P+error in Q/Q
    error in x=0.01..
    therefore %age uncertainty in x=(0.01/0.44)x100=2.2%..
    therefore %age uncertainty in x=2.2%..
    hope this helps :)
     
  9. MysteRyGiRl

    MysteRyGiRl

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    ummm da answer 4 da second question is supposed 2 b 7% :shock:
    hw do v get dat???
    btw thnx 4 helping out
     
  10. Xenon

    Xenon

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    maybe thundering thunder made a typing mistake, the error in x will be 0.03 (0.02 + 0.01 )instead on 0.01. this will give u a value of 6.8%.
     
  11. MysteRyGiRl

    MysteRyGiRl

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    ohhhkk :)
    thanx guyzz :)
     
  12. thunderingthunder

    thunderingthunder

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    YEAH!!i agree---> :D :D :D
     

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