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We want to relate the small
length, area, or volume element

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00:00:05,510 --> 00:00:09,370
to delta m, the amount
of mass contained within.

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00:00:09,370 --> 00:00:11,270
In one dimension,
this relation is

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called the linear
density, lambda,

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which is delta m over delta l.

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00:00:17,370 --> 00:00:22,040
For a uniform rod of
length L and total mass M,

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lambda is equal to M over
L. In two dimensions,

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the area element contains an
amount of mass sigma times

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00:00:31,370 --> 00:00:36,060
delta A, where sigma has
units of mass over area.

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00:00:36,060 --> 00:00:40,400
Finally, in three dimensions,
the volume density rho

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connects the small mass, delta
m, to the volume, delta V.