JEE Main & Advanced Physics Rotational Motion Question Bank Self Evaluation Test - System of Particles Rotational Motion

  • question_answer
    A horizontal turn table in the form of a disc of radius r carries a gun at G and rotates with angular velocity \[{{\omega }_{0}}\] about a vertical axis passing through the centre O. The increase in angular velocity of the system if the gun fires a bullet of mass m with a tangential velocity v with respect to the gun is (moment of inertia of gun + table about 0 is \[{{I}_{0}}\])      

    A) \[\frac{mvr}{{{I}_{0}}+m{{r}^{2}}}\]

    B) \[\frac{2mvr}{{{I}_{0}}}\]

    C) \[\frac{v}{2r}\]

    D) \[\frac{mvr}{2{{I}_{0}}}\]

    Correct Answer: A

    Solution :

    [a] Given that \[{{I}_{0}}\] is the moment of inertia of table and gun and m the mass of bullet. Initial angular momentum of system about centre \[{{L}_{i}}({{I}_{0}}+m{{r}^{2}}){{\omega }_{0}}\]                                  ? (i) Let w be the nagular velocity of table after the bullet is fired. Final angular momentum \[Lf=({{I}_{0}}\omega -m(v-r\omega )r\]                    ? (ii) Where (\[v-r\omega \]) is absolute velocity of bullet to the right. Equations (i) and (ii); we get \[(\omega -{{\omega }_{0}})=\frac{mvr}{{{I}_{0}}+m{{r}^{2}}}\]


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