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Homework Help: Propagation of errors addition numbers without uncertainty

  1. Oct 4, 2011 #1
    1. The problem statement, all variables and given/known data
    I am having trouble calculating uncertainty when a number is added to a value with uncertainty.

    M = 350g
    a = 0.624 [itex]\pm[/itex] 0.001
    µk = 0.07
    g = 9.80 m/s2

    2. Relevant equations
    T = M*a + µk*M*g

    3. The attempt at a solution
    T = (350g)*(0.624 m/s2) + (0.07)*(350g)*(9.80m/s2)
    T= 458.5 N
    D[itex]_{}t[/itex] = M*(D[itex]_{}a[/itex]) + ......
    D[itex]_{}t[/itex] = (350g)*(0.001 m/s2) + ......
    D[itex]_{}t[/itex] = 0.35 N + ....
  2. jcsd
  3. Oct 4, 2011 #2


    User Avatar

    Staff: Mentor

    If you're given that there is no uncertainty in M, g, or µk then you treat them as constants that are 100% accurate. The uncertainty in the result, then, only depends upon the uncertainty in a, as you've written. The uncertainty in the µk*M*g term is zero.
  4. Oct 4, 2011 #3
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