In college physics, how to find a thin disk, in which the axis of rotation is perpendicular to the disk surface through the center of the circle, and how to find the moment of inertia of this disk? th

Take the graph infinitesimal, and the infinitesimal area dS=rdrdθ.

Infinitely small mass dm=(m/πR? )dS=(m/πR？ )rdrdθ

Moment of inertia of disk J=∫∫dmr? =(m/πR？ )∫∫r？ drdθ=(m/πR？ )∫dθ∫r？ Doctor?

Substitution? θ integration interval 0-2 π,,, r integration interval 0-r integration can be obtained:

J=mR？ /2

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