A thin ring of mass M and radius r rotates at angular speed ω. Four particles each mass m are placed gently at the opposite ends of two perpendicular diameters. Find final angular speed.
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Question

A thin ring of mass M and radius r rotates at angular speed ω. Four particles each mass m are placed gently at the opposite ends of two perpendicular diameters. Find final angular speed.

G1 Physics · Accepted Answer

Step 1: Initial angular momentum is Mr²ω. Step 2: Final inertia is (M+4m)r². Step 3: Conservation yields ωf=Mω/(M+4m). Final answer: B — Mω/(M+4m).