All bounded orbits where the gravity of a central body is strong are elliptical in nature. An example of this is the circular orbit, which is an ellipse of zero eccentricity.
The formula for the velocity of a body in a circular orbit at distance r from the centre of gravity of mass M is given as,
To properly use this formula, the units must be consistent – M must be in kilograms, and r must be in meters
v = velocity
G = gravitational constant
M = mass of the body
r = distance from the centre of gravity of mass M