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

A disk of moment of inertia I and angular velocity ω is dropped onto another stationary disk with the same I. They eventually reach the same speed due to friction. Final ω is:

Answer: ω/2.

A ω/2
B ω
C 2ω
D ω/√2

Correct answer: A. ω/2

Explanation: By conservation of angular momentum (friction is internal between the two disks): Iω = 2Iω_f → ω_f = ω/2.

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 disk of moment of inertia I and angular velocity ω is dropped onto another stationary disk with the same I. They eventually reach the same speed due to friction. Final ω is:

Concept context

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