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| Physical Meaning of Angular Momentum |
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Consider a particle capable of rotation about an axis. At any time t, let
its momentum be  and  ,
the position vector. Then the angular momentum is given by the cross product
and .
 =
x . |
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| In three dimensions, |
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| Lx = ypz - zpy, Ly = zpx - xpz, Lz = xpy - ypx. |
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| The angular momentum, which is nothing but moment of linear momentum, can be expressed in terms of the lever arm for momentum. |
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| Let us consider the case of angular momentum in two dimensions. |
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| L = xpy - ypx |
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| If j
is the angle between
and x-axis, then px = p cos y and py
= p sin y. Also x =
r cos q, y =
r sin q. |
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| Hence, we can define angular momentum as the product of linear momentum and the lever arm for momentum. |
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| Let pr and pq be the radial and angular components of linear momentum respectively . The radial component pr will not contribute anything to L. The only effective component is pq. |
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| Here, we see some similarity between angular momentum and torque. Both of them depend on the location of the particle in a similar way. If torque is the measure of the turning effect of the force, angular momentum is a measure of the turning movement of the object. |
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