Assumptions - Energy and Orbits

The applet simulates the gravitational potential energy of a satellite-earth system or projectile-earth system along with the satellite's or projectile's kinetic energy and the total mechanical energy of the system.

The applet makes the following assumptions:

The earth is a perfect sphere with radius R = 6.378×10³ km.
The mass density is uniform throughout the earth.
The acceleration due to gravity at the surface of the earth has the magnitude g = 9.805 m/s².
The projectile or satellite is subject only to the earth's gravitational force, not to air resistance or any other kind of force.
The earth is not rotating about its axis.
Put differently, the applet simulates the motion of a satellite or projectile relative to a coordinate system that is held fixed relative to the fixed stars (inertial frame of reference), and the rotation of the earth relative to this system is not simulated.

A consequence of the first two assumptions is that the force of gravity exerted by the earth on an object above the surface of the earth is the same as that exerted by a point particle whose mass is equal to that of the earth and which is located at the center of the earth.

The last assumption implies that the motion of a projectile relative to an earth-fixed coordinate system (rotating non-inertial reference frame) is simulated without the Coriolis and centrifugal forces. These fictitious forces would affect the motion of a projectile relative to an earth-fixed set of axes in the realistic case in which the earth is rotating.