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Homework Help: A star that changed size

  1. Jan 15, 2010 #1
    1. The problem statement, all variables and given/known data

    A star of mass 1.81×1031 kg and diameter 8.10E+9 m rotates with a period of 25.0 days. Suddenly the star changes size, and rotates with a new period of 18.0 days. Assuming a uniform density both before and after the size change, what is the new diameter of the star?

    2. Relevant equations

    Volume = 4/3*3.14*R^3
    Density = M / VOL
    I =2/5*M*R^2

    3. The attempt at a solution

    R(initial) = 8.10*10^9/2=4.05*0^9
    Volume(initial) = 4/3*3.14*(4.05*10^9)^3=2.782*10^29
    Density= (1.81*10^31/(2.782*10^29)=65.061

    the computer said that this answer is wrong and i don't know why
    Last edited: Jan 15, 2010
  2. jcsd
  3. Jan 15, 2010 #2


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    Homework Helper

    109.01 is not right. Try recalculating that number.
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