10C's: C1
     [See lectures, class web pages, HWs & solutions, and Chapter 5 of TB1.]
C1: G, Newton's gravitational constant,
    & his three laws of motion & his universal law of gravity
    * Newton's three laws of motion;
    * Newton's universal law of gravity: The gravitational force between two massive objects is proportional to the product of the two (rest) masses, and is inversely proportional to the square of the distance between them, and the proportional constant is Newton's constant of gravity..
        ** Units of G;
    * Angular momentum is conserved
        ** Equation for angular momentum;.
    * Energy in Newtonian mechanics is composed of kinetic energy (one for each dimension of the space) and potential energy (due to the gravitational force in the direction of the pull only)
            ** Equations for  kineticenergies, one for each dimension of the space:
                    *** kinetic energy in the radial direction;
                    *** kinetic energy in the angular direction;
                    *** kinetic energy in the 3rd direction (the direction perpendicular to the above two) = 0.
            ** Gravitation potential energy (negative)
                    *** Exact equation;
                    *** Exact equation for the difference of two potential energies.
                    *** Approximate equation derived from exact equation for the difference of two potential energies at different heights.
    * Escape velocity is the velocity at which the sum of the kinetic energy (positive) and the gravitational potential energy (negative) is zero.