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Homework Help: Calculating uncertainty in a problem?

  1. Apr 15, 2010 #1
    Calculating uncertainty in a problem??

    Hi I have a quick question:

    You drop a ball(with zero initial velocity) from the top of a building. If you measure the acceleration to be 9.8 +/- 0.1 m/s^2 and the height of the building to be 30 +/- 1 m, what is the final velocity?

    So you would use the equation
    V(final)^2 = V(initial)^2 +2ad

    v= [(2)(9.81)(30)]^0.5
    v=24.249 m/s

    Can you explain how to determine the uncertainty of the answer? Thank you!

    The ANSWER given was : 24.2 +/- 0.5 m/s
  2. jcsd
  3. Apr 15, 2010 #2
    Re: Calculating uncertainty in a problem??

    I have tried and this works... but it might have been coincidence.. (can someone verify and possibly direct me to (or tell me) the basic rules when determining uncertainties)

    using the MAX values (ie, a=9.9 and d=31)
    the answer is 24.77

    using the MIN values (ie, a=9.7 and d=29)
    the answer is 23.72

    then: (24.77-23.72)/2 = 0.525 <-- uncertainty

    Is this process completely incorrect? How do you determine uncertainty?
    Please help!
  4. Apr 16, 2010 #3
    Re: Calculating uncertainty in a problem??

    help? :(
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