System of Particles and Rotational Motion - Result Question 42

45. A thin circular ring of mass M and radius r is rotating about its axis with a constant angular velocity ω. Four objects each of mass m, are kept gently to the opposite ends of two perpendicular diameters of the ring. The angular velocity of the ring will be

[2003]

(a) (M4m)ωM+4m

(b) Mω4m

(c) MωM+4m

(d) (M+4m)ωM

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Answer:

Correct Answer: 45. (c)

Solution:

  1. (c) Applying conservation law of angular momentum, I1ω1=I2ω2

I2=(Mr2)+4(m)(r2)=(M+4m)r2

. (Taking ω1=ω and ω2=ω1)Mr2ω=(M+4m)r2ω1ω1=MωM+4m



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