⚛️ Physics · System of Particles and Rotational Motion · NEET & JEE

A point mass m is attached to the end of a string and rotates in a horizontal circle of radius r. The angular momentum about the centre is L = mvr. If r is halved and v is doubled, L becomes:

Answer: L.

A L
B 2L
C L/2
D 4L

Correct answer: A. L

Explanation: L' = m(2v)(r/2) = mvr = L. Angular momentum remains the same.

Torque about axis O equals the force F multiplied by the perpendicular distance r⊥ from the axis to the line of action of the force, producing rotation.

Concept context

Moment of inertia, torque, angular momentum, rolling motion. Very high JEE weightage.

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A point mass m is attached to the end of a string and rotates in a horizontal circle of radius r. The angular momentum about the centre is L = mvr. If r is halved and v is doubled, L becomes:

Concept context

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