Rotational Motion

The angular momentum of a planet moving around the sun in a circular orbit is given by: where is the mass of the planet, is the radius of the orbit, and is the tangential velocity of the planet.
The areal velocity of the planet is defined as the rate at which the area swept out by the radius vector changes. It is given by: For a circular orbit, the areal velocity is constant and is related to the angular momentum by: Therefore, the areal velocity of the planet about the center of the sun is: Thus, the areal velocity of the planet is .