Question

A mass $M$ is moving with constant velocity parallel to $x$-axis. Its angular momentum about the origin

• A. is zero.
• B. increases.
• C. decreases.
• D. remains constant.

Answer 1

Answer: (D)

remains constant.

The angular momentum is the moment of the linear momentum $mv$.
$\overrightarrow{L}=\overrightarrow{r}\times \overrightarrow{p}=mvr\sin \theta =mv(\perp distancefromx-axis)$
The $\perp$ distance from the $x$-axis is constant.
$\therefore$ $\overrightarrow{L}$ is constant.