Rotational Motion

JEE Main level, single correct, medium

170 of 280

Question 170 of 280

A uniformly thick wheel with moment of inertia II and radius RR is free to rotate about its centre of mass (see fig). A massless string is wrapped over its rim and two blocks of masses m1{m}_{1} and m2(m1>m2){m}_{2}\left({m}_{1}\gt {m}_{2}\right) are attached to the ends of the string. The system Is released from rest. The angular speed of the wheel when m1{m}_{1} descends by a distance hh is:

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Answer: (A) [2(m1−m2)gh(m1+m2)R2+I]12{\left[\dfrac{2\left({m}_{1}-{m}_{2}\right)gh}{\left({m}_{1}+{m}_{2}\right){R}^{2}+I}\right]}^{\dfrac{1}{2}}

TEi=TEfKi+Ui=Klinear+Krotational+UfinalT{E}_{i}=T{E}_{f} {K}_{i}+{U}_{i}={K}_{linear}+{K}_{rotational}+{U}_{final}
0+0=12m2v2+12m1v2+12Iω2−m1gh+m2gh0+0=\dfrac{1}{2}{m}_{2}{v}^{2}+\dfrac{1}{2}{m}_{1}{v}^{2}+\dfrac{1}{2}I{\omega }^{2}-{m}_{1}gh+{m}_{2}gh
2(m1−m2)gh(m1+m2+IR2)R2=ω\sqrt{\dfrac{2\left({m}_{1}-{m}_{2}\right)gh}{\left({m}_{1}+{m}_{2}+\dfrac{I}{{R}^{2}}\right){R}^{2}}=\omega }
1R2(m1−m2)gh(m1+m2+IR2)\dfrac{1}{R}\sqrt{\dfrac{2\left({m}_{1}-{m}_{2}\right)gh}{\left({m}_{1}+{m}_{2}+\dfrac{I}{{R}^{2}}\right)}}

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