Answer
* Angular momentum about a point on the line - No
* Angular momentum about a point not on the line - Yes
* Angular momentum is constant about a point not on the line
Work Step by Step
* The particle hasn't an angular momentum about a point on the line. Because if we use the right-hand rule, there is no angular velocity in the direction of the angular momentum. So there isn't an angular momentum.
* The particle has an angular momentum about a point, not the line. Because there is an angular velocity in the direction of the angular momentum.
* Please see the attached image first.
We know that the angular momentum of a particle, $L=mrV$
Let's consider incident (1),
$L_{1}=mR_{1}Vcos\alpha=mR_{1}V\times\frac{L}{R_{1}}=mLV-(1)$
Let's consider incident (2),
$L_{2}=mLV-(2)$
Let's consider incident (1),
$L_{3}=mR_{2}Vcos\alpha=mR_{2}V\times\frac{L}{R_{2}}=mLV-(3)$
(1)=(2)=(3),
$L_{1}=L_{2}=L_{3}$ ; Angular momentum is constant
