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| Geometrical Meaning and Conservation of Angular Momentum |
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Consider a particle A having linear
momentum  and radius
vector  with respect to the
origin as given in the figure. After a time Dt,
the particle is at B and the radius vector becomes
+ D. |
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The velocity  of the
particle has a radial component vr and an angular component vf.
So pr and pq are the radial and
angular momenta, |
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| This is the geometrical significance of angular momentum. |
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| Kepler's second law |
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In the case of a planet, moving around the sun in an elliptical orbit with the sun at one of the foci of the ellipse, the gravitational force always acts along the line joining the planet with the sun. Thus, the force is always radial or the angular component  of the force is always zero. |
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 L = Angular momentum = constant |
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| Hence, if angular momentum remains constant, areal velocity should also remain constant. Kepler's second law states that, area swept by the radius vector of the planet in equal intervals of time is same or in other words, areal velocity of the planet is constant. |
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