text: Circular acceleration Transverse acceleration (perpendicular to velocity) causes a change in direction. If it is constant in magnitude and changing in direction with the velocity,  circular motion ensues. Taking two derivatives of the particle's coordinates concerning time gives the centripetal acceleration
  where:
  is the orbital velocity of the orbiting body,
  is radius of the circle
  is angular speed, measured in radians per unit time.
  The formula is dimensionless, describing a ratio true for all units of measure applied uniformly across the formula. If the numerical value  is measured in meters per second squared, then the numerical values  will be in meters per second,  in meters, and  in radians per second.
  Velocity
  The speed (or the magnitude of velocity) relative to the central object is constant:
  where:
  , is the gravitational constant
  , is the mass of both orbiting bodies , although in common practice, if the greater mass is significantly larger, the lesser mass is often neglected, with minimal change in the result.
  , is the standard gravitational parameter.
  Equation of motion
  The orbit equation in polar coordinates, which in general gives r in terms of θ, reduces to:
  where:
  is specific angular momentum of the orbiting body.
  This is because
  Angular speed and orbital period
  Hence the orbital period () can be computed as: