Question

A particle of mass $m$ is moving with constant velocity $v$ parallel to the $x-$axis as shown in the figure. Its angular momentum about origin $O$ is

• A. $mvb$
• B. $mva$
• C. $mv\sqrt{a^2+b^2}$
• D. $mv(a+b)$

Answer 1

The correct option is A $mvb$

Velocity $=v\hat{i}$

position vector $=a\hat{i}+b\hat{j}$

Angular momentum $=m(a\hat{i}+b\widehat{)}\times v\hat{i}$

and on doing cross product

$=mvb\hat{k}$ is the angular momentum of the particle

which represents in the direction of z-axis

In scalar form

$=mvb$

Hence, option $A$ is the correct answer.