Question

A body is moving with constant velocity parallel to x-axis. Its angular momentum w.r.t. the origin will :

• A. be zero
• B. decrease
• C. increase
• D. remain constant

Hint:

If no external force or torque acts, angular momentum is conserved.

Answer 1

The Correct Option is D

Concept: Angular momentum: \[ \vec{L} = \vec{r} \times \vec{p} \] If no external torque acts, angular momentum remains constant.

Step 1: Direction of motion.
Velocity is constant and parallel to x-axis.

Step 2: Torque about origin.
\[ \vec{\tau} = \frac{d\vec{L}}{dt} \] Since no force is acting (constant velocity), net torque is zero.

Step 3: Conclusion.
\[ \vec{L} = \text{constant} \]