### specific angular momentum

**(J)**
(absolute angular momentum divided by mass)

The **specific angular momentum** (**J**) of an orbiting body
is its angular momentum divided by its mass,
i.e., the angular momentum per unit mass.

J = L/m

- J - specific angular momentum.
- L - angular momentum.
- m - mass.

The decision as to which mass may depend upon
the use to which it will be put.

**Angular momentum** is a "momentum" associated
with rotation and is represented as a vector
along the axis of rotation, with a vector magnitude
representing the degree/amount. For a point
circling an axis, it is:

L = rmv

- L - angular momentum.
- r - radius of rotation.
- m - mass of the particle.
- v - magnitude of the velocity of the particle.

Conventionally, the choice of directions along the
axis uses the **right hand rule**. Following this convention
allows the vectors to be added to calculate the angular
momentum of multiple points fixed to each other as a rigid
structure. The "right handedness" in its definition
is an arbitrary choice, but makes things consistent.

**Angular momentum** is conserved. If you begin spinning yourself,
the Earth's spin is very slightly modified in the other direction
so the total angular momentum including you and the Earth has not
changed.

(*dynamics,measure*)
http://scienceworld.wolfram.com/physics/SpecificAngularMomentum.html

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