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Homework Help: Two worlds spinning

  1. Nov 6, 2008 #1
    1. The problem statement, all variables and given/known data

    There are two balls with masses m_a and m_b connected by a string. m_b is moving at a velocity v upwards (perpendicular to the string) and it asks for the Tension (T) in the string.

    2. Relevant equations

    delta Energy of system = 0

    T = m((u^2)/r)
    u is linear speed of rotational motion
    r = radius of motion

    3. The attempt at a solution

    The initial kinetic energy of m_b = .5(m_b)v^2

    and that's as far as I got.
    Is mass B moving?

    how do I start this problem?

    Attached Files:

  2. jcsd
  3. Nov 6, 2008 #2

    Doc Al

    User Avatar

    Staff: Mentor

    That will come in handy.
    Why did you calculate the energy?

    Mass B's velocity is described in the problem statement.

    Hint: Viewed from the inertial lab frame, mass B is in pure rotation about mass A (at the instant shown). Apply Newton's 2nd law.
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