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Physics 250 Problem: Help

  1. Nov 16, 2005 #1
    If the size of a new Kuiper object is 0.0150 arc sec in angular size as seen from a distance of 42.00 AU, what is the true diameter? If it has a satellite with a period of 5.50 hours at a semimajor axis of 12500.0 km, what is the mass? What is the resulting density? What do you it is composed of?

    What I know:
    I know that I use V=4/3(pi)r^3 to get the density and previous equations to solve for mass. I don't know how I am supposed to apply the 0.0150 arc seconds or distance to solve for the diameter. What is the equation for that?
  2. jcsd
  3. Nov 16, 2005 #2


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    Staff: Mentor

    What is the relationship of the some length of segment on the circumference of a circle and the angle subtended by that segment?
  4. Nov 16, 2005 #3
    I have no idea what you mean when you say "angle subtended..."
  5. Nov 16, 2005 #4
    Is the concept of angular size the trouble here. Here is a diagram, with this you should know what to do...

    So the furthur away the object is, the smaller the angular size will become.

    Hope this helps...
    Last edited: Nov 16, 2005
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