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Q.
A particle is moving along a straight line parallel to $x$ -axis with constant velocity. Its angular momentum about the origin
System of Particles and Rotational Motion
Solution:
Suppose the particle of mass $m$ is moving with speed
$v$ parallel to $x$ axis as shown in figure, then
at any time $t$, coordinates of $P$ will be
$x=v t, y=b$ and $z=0$
while components of velocity will be
$v_{x}=v, v_{y}=0$ and $v_{z}=0$
(as it is moving parallel to $x$ -axis)
l.e., angular momentum has magnitude $m v b$ and is directed
along negative $z$ -axis, i.e., angular momentum remains constant.
