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Homework Help: Mass sliding down surface of a sphere

  1. Feb 21, 2012 #1
    1. The problem statement, all variables and given/known data

    A small mass m slides down from rest at the top of a frictionless spherical surface of radius R=.5 meters. What is the speed of the particle at position x where it loses contact with the surface, and velocity makes an angle of θ=48.2 with the vertical?

    The answer choices are:

    (A) 1.28 m/s
    (B) 1.82 m/s
    (C) 1.93 m/s
    (D) 2.36 m/s
    (E) 2.58 m/s

    2. Relevant equations

    Conservation of Energy?

    3. The attempt at a solution

    I thought maybe start with PE1=PE2+KE, where h=2r, and then find the cosine component of the height when velocity is at that angle, to do: mg(2r)=(1/2)mv2+mg((cos48.2)+R), but that didn't work. I got .57, which is not even close to any of the choices.
  2. jcsd
  3. Feb 21, 2012 #2


    User Avatar
    Science Advisor
    Homework Helper

    Hi Victorzaroni! :smile:
    I think you missed out the 9.8 :wink:

    (also, read the question carefully about the angle)
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