Can an object moving in a straight line have angular momentum?

The position vector of a particle of mass $m$ moving with a constant velocity $\vec{v} = v \hat{i}$ is given by $\vec{r} = x(t) \hat{i} + b \hat{j}$, where $b$ is a constant. At an instant, $\vec{r}$ makes an angle $\theta$ with the $x$-axis. The variation of the magnitude of the angular momentum $|\vec{L}|$ of the particle about the origin with $\theta$ will be:

Explain the Cartesian components of the angular momentum of a particle.

Identify the vector quantity among the following.

$A$ particle of mass $2\, kg$ is on a smooth horizontal table and moves in a circular path of radius $0.6\, m$. The height of the table from the ground is $0.8\, m$. If the angular speed of the particle is $12\, rad\, s^{-1}$,the magnitude of its angular momentum about a point on the ground right under the centre of the circle is ........ $kg\, m^2\, s^{-1}$.

$A$ uniform rod of mass $m$ and length $l$ is moving with velocity $u$ in a direction perpendicular to its length. $A$ blow of impulse $J$ is applied in the direction of $u$,perpendicular to its length at a distance $l/4$ from its center at point $P$,such that the instantaneous velocity of point $P$ is $2u$. Then the velocity of its center of mass will be: