Encyclopedia of Astrobiology

Living Edition
| Editors: Muriel Gargaud, William M. Irvine, Ricardo Amils, Henderson James Cleaves, Daniele Pinti, José Cernicharo Quintanilla, Michel Viso

Angular Momentum

  • Jérôme Perez
Living reference work entry
DOI: https://doi.org/10.1007/978-3-642-27833-4_79-3


In mechanics, angular momentum is the vector cross product between the position vector and the momentum vector of a point mass system. This definition can be extended to a solid by summation.


The movement of a point mass m is defined by its position r and its velocity v. These quantities are vectors relative to some reference system. This movement splits into two parts: a movement of translation and a movement of rotation. The amount of movement is measured by the linear momentum (impulsion) p = mv (for simple cases), which is a conserved quantity for a translation invariant system. The amount of rotation is measured by the angular momentum L = r × p, which is a conserved quantity for a rotation invariant system. Note that the vector cross product \( \boldsymbol{a}\times \boldsymbol{b}= ab\; \sin \theta\;\boldsymbol{n} \)


Rotating body 
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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.Applied Mathematics LaboratoryENSTA ParisTechParis cedex 15France