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Homework Help: Circular Motion Lab with Hanging Mass - Trying To Find Centripetal Force

  1. Nov 21, 2009 #1
    Sorry if this is posted in the wrong area, I am relatively new.

    Circular Motion Lab is set up like this to study circular motion:

    http://docs.google.com/viewer?a=v&q=cache:lG3nvirsnOYJ:www.hwscience.com/Physics/regphysics/Lab%2520Handouts/Circ.%2520motion%2520LAB.pdf+circular+motion+hanging+mass&hl=en&gl=ca&sig=AHIEtbTBHCVNZxCFmkJyfcwpOLkbKJl59w [Broken]

    Rubber stopper is secured to string .4m long, and is spun horizontally and achieves period of 0.56275s. The hanging mass is 0.03kg. The mass of the stopper is unknown.

    I figured out that Centripetal velocity is 4.466m/s.

    The vertical forces is Fnet = Ft - Fg

    Ft= Fnet + Fg
    Ft = m(a + g)
    Ft= 0.03 (9.81)
    Ft= 0.2943

    The horizontal forces are Fc = Ft
    Fc= 0.2943 N !!!!!!!!!!

    Is this done RIGHT to FIND the centripetal FORCE of the rubber STOPPER?
    Please explain if I am wrong...
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Nov 21, 2009 #2


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    Homework Helper

    You must consider the angle of droop in your force diagram. Tension is certainly not a vertical force - it is PARTLY vertical and partly horizontal. You'll have sin A and cos A in your expressions when you separate T into horizontal and vertical parts.
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