Question

A particle is moving uniformly along a straight line as shown in the figure. During the motion of the particle from A to B, the angular momentum of the particle about ‘O’

• A. remains constant
• B. increases
• C. first increases then decreases
• D. decreases

Answer 1

Answer: (A)

Angular momentum $L=mvr$
where $r$ is the perpendicular distance between velocity and reference point Here since the line $AB$ is straight, there would only 1 perpendicular distance from reference point i.e OA
So,
Angular momentum at $A=mvr$
Angular momentum at $P=mvr$
Angular momentum at $B=mvr$
Since, perpendicular distance between the line $AB$ and $O$ will always be $R$ So all the points lying on the line $AB$ will have same angular momentum equals to mvr.