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{\bf Introduction to Astrophysics I, 29:119\\
     Fall, 2008\\
First Homework Set...August 28, 2008. Due September 04, 2008}\\
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Show calculations and give reasons for your answers. Don't go around 
confused and despondent; if you do not know how to get started, ask me for help. The purpose
of problem sets is to promote thinking and lead to understanding, not 
produce a {\em confiteor} of revealed truth.\\

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{\bf (1)} Find orbital data for the planets in the solar system.  Calculate the minimum distance that can occur between the Earth and the planet Mars.  Then calculate the maximum distance between the two. \\

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{\bf (2)} The Earth-Sun system can be considered as an example of the 2 body problem.  Calculate the distance from the center of the Sun to the center of mass of the Earth-Sun system.  Then calculate the accelerations of the Sun and Earth due to the gravitational force between them.  Finally, approximating the true orbits by circular orbits ( a very good approximation in this case), calculate the speeds at which the Earth and Sun move in their orbits about their center of mass.  \\

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{\bf (3)}  Problem 2.1 from textbook.\\

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{\bf (4)} Problem 2.2 from textbook. \\ 

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{\bf (5)}  Using equations developed in class, demonstrate that the gravitational force of a circularly symmetric distribution of mass in a disk on a point mass in the plane of the disk, but beyond its edge is {\em not} the same as if all the mass were concentrated in a point mass at the center of the disk (i.e. the result differs from that of a sphere).  You can use either a program such as Mathematica or MathCad (recommended) or analytic methods. \\

 
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