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Homework Help: An object attached by two strings on a vertical rod travels at a constant velocity

  1. Jun 24, 2012 #1
    1. The problem statement, all variables and given/known data
    BtMla.png
    **Hope I don't get in trouble for posting a screenshot of this online homework question...**

    2. Relevant equations
    [itex]\Sigma[/itex]Fx = marad = [itex]\frac{mv^2}{r}[/itex]
    [itex]\Sigma[/itex]Fy = mg


    3. The attempt at a solution
    Simple equations allowed me to find r = 1.323m and θ = 41.41°
    [itex]\Sigma[/itex]Fx = Tuppersinθ + Tlowersinθ + mgsinθ = [itex]\frac{mv^2}{r}[/itex]
    Tuppersinθ + Tlowersinθ + 28.85N = 169.57N
    Tupper + Tlower = 212.75N

    [itex]\Sigma[/itex]Fy = Tuppercosθ - Tlowercosθ - mg = 0
    Tuppercosθ - Tlowercosθ = mg
    Tupper - Tlower = 58.15N
    Tupper = 58.15N + Tlower

    Substituting Tupper,
    58.15N + Tlower + Tlower = 212.75N
    58.15N + 2(Tlower) = 212.75N
    Tlower = 77.3N
    Tupper = 58.15N + 77.3N = 135.45N
     
    Last edited: Jun 24, 2012
  2. jcsd
  3. Jun 24, 2012 #2

    Doc Al

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    Staff: Mentor

    Re: An object attached by two strings on a vertical rod travels at a constant velocit

    Good.
    In what direction does the weight act?
     
  4. Jun 24, 2012 #3
    Re: An object attached by two strings on a vertical rod travels at a constant velocit

    Away from the pole, so I guess mgsinθ is negative as well?

    EDIT: Ah, nope. Fx is only mv^2/r, so I don't need to take into account the gravitational force. Got the answers, thanks for your help!
     
    Last edited: Jun 24, 2012
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