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Circular motion and gravity help

  1. Jun 8, 2013 #1
    1. The problem statement, all variables and given/known data

    1. The mass of a star is 1.830×1031 kg and it performs one rotation in 37.30 days. Find its new period (in days) if the diameter suddenly shrinks to 0.850 times its present size. Assume a uniform mass distribution before and after.

    2. A pulley with mass Mp and a radius Rp is attached to the ceiling, in a gravity field of 9.81 m/s2 and rotates with no friction about its pivot. Mass M2 is larger than mass m1. The quantities Tn and g are magnitudes. Choices: true, false, greater than, less than, or equal to.

    The C.M. of Mp+M1+M2 does not accelerate.
    T1 is ..... T2
    m1g + M2g + Mpg is ..... T3.
    T3 is ..... T1 + T2
    T2 is ..... M2g.
    The magnitude of the acceleration of M2 is ..... that of m1.

    2. Relevant equations

    T=mg

    3. The attempt at a solution

    do not know how to go about solving either of these :(
     
  2. jcsd
  3. Jun 8, 2013 #2
    Don't post two different problems in one thread. I am not sure this is strictly against the rules, but it makes things very confusing.
     
  4. Jun 8, 2013 #3
    the second question is just conceptual so i had hoped it wouldnt make things to confusing, im sorry
     
  5. Jun 8, 2013 #4
    It may be, but you ignored the template requirements for the first question.
     
  6. Jun 8, 2013 #5
    i know, its because i dont even know what equation to use for it, no one can seem to figure out how to solve it...
     
  7. Jun 8, 2013 #6
    What properties of rotating bodies do you know about, especially those that are conserved?
     
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