JEE Main & Advanced JEE Main Paper Phase-I (Held on 09-1-2020 Evening)

  • question_answer
    A uniformly thick wheel with moment of inertia I and radius R is free to rotate about its centre of mass (see fig.), A massless string is warapped over its rim and two blocks of masses \[{{m}_{1}}\] and \[{{m}_{2}}({{m}_{1}}>{{m}_{2}})\] are attached to the ends of the string. The system is released from rest. The angular speed of the wheel when \[{{m}_{1}}\]descents by a distance h is [JEE MAIN Held on 09-01-2020 Evening]

    A) \[{{\left[ \frac{({{m}_{1}}-{{m}_{2}})}{({{m}_{1}}+{{m}_{2}}){{R}^{2}}+I} \right]}^{\frac{1}{2}}}gh\]

    B) \[{{\left[ \frac{2({{m}_{1}}-{{m}_{2}})gh}{({{m}_{1}}+{{m}_{2}}){{R}^{2}}+I} \right]}^{\frac{1}{2}}}\]

    C) \[{{\left[ \frac{{{m}_{1}}+{{m}_{2}}}{({{m}_{1}}+{{m}_{2}}){{R}^{2}}+I} \right]}^{\frac{1}{2}}}gh\]

    D) \[{{\left[ \frac{2({{m}_{1}}+{{m}_{2}})gh}{({{m}_{1}}+{{m}_{2}}){{R}^{2}}+I} \right]}^{\frac{1}{2}}}\]

    Correct Answer: B

    Solution :

    \[\Delta K+\Delta U=0\] \[\frac{1}{2}{{m}_{1}}{{v}^{2}}+\frac{1}{2}{{m}_{2}}{{v}^{2}}+\frac{1}{2}I\frac{{{v}^{2}}}{{{r}^{2}}}=({{m}_{1}}-{{m}_{2}})gh\] \[v=\sqrt{\frac{2({{m}_{1}}-{{m}_{2}})gh}{{{m}_{1}}+{{m}_{2}}+\frac{1}{{{r}^{2}}}}}\] \[w=\frac{V}{r}\]


You need to login to perform this action.
You will be redirected in 3 sec spinner