The lower-case letter q is used for a number of different purposed in physics. It is commonly used to denote the deceleration parameter, a generalized coordinate, or the oblateness constant. In celestial mechanics, q is defined for a parabolic orbit as
where h is the specific angular momentum, G is the gravitational constant, M is the
mass of the central body, and mu is defined by
Deceleration Parameter, Generalized Coordinate, Oblateness Constant, Parabolic Orbit, Q
