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A thin circular ring of mass M and radius R is rotating in a horizontal plane about an axis vertical to its plane with a constant angular velocity \omega. If two objects each of mass m be attached gently to the opposite ends of a diameter of the ring, the ring will then rotate with an angular velocity

  • Option 1)

    \frac{\omega M}{M+2m}

  • Option 2)

    \frac{\omega (M+2m)}{M}

  • Option 3)

    \frac{\omega\: M}{M+m}

  • Option 4)

    \frac{\omega (M-2m)}{M+2m}

 

Answers (1)

best_answer

As discussed in

Law of conservation of angular moment -

vec{	au }= frac{vec{dL}}

- wherein

If net torque is zero

i.e. frac{vec{dL}}= 0

vec{L}= constant

angular momentum is conserved only when external torque is zero .

 

 L_{i}=L_{f}

I_{1}\omega=I_{2}\omega'

MR^{2}\omega=(M+2m)R^{2}\omega'

\omega'=\frac{M \omega}{M+2m}


Option 1)

\frac{\omega M}{M+2m}

This option is correct.

Option 2)

\frac{\omega (M+2m)}{M}

This option is incorrect.

Option 3)

\frac{\omega\: M}{M+m}

This option is incorrect.

Option 4)

\frac{\omega (M-2m)}{M+2m}

This option is incorrect.

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Plabita

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