Rotational Motion

JEE Main level, numerical answer, medium

256 of 280

Question 256 of 280

Two bodies, a ring and a solid cylinder of same material are rolling down without slipping an inclined plane. The radii of the bodies are same. The ratio of velocity of the centre of mass at the bottom of the inclined plane of the ring to that of the cylinder is x2.\dfrac{\sqrt{x}}{2}. Then, the value of xx is

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Answer: 3

In both, cases is about point of contact ring,
mgh=12Iω2mgh=\dfrac{1}{2}I{\omega }^{2}
mgh=12(2mR2)VR2R2mgh=\dfrac{1}{2}\left(2m{R}^{2}\right)\dfrac{{V}_{R}^{2}}{{R}^{2}}
VR=gh{V}_{R}=\sqrt{gh}
Solid cylinder

mgh=12Iω2mgh=\dfrac{1}{2}I{\omega }^{2}
mgh=12(32mR2)vC2R2mgh=\dfrac{1}{2}\left(\dfrac{3}{2}m{R}^{2}\right)\dfrac{{v}_{C}^{2}}{{R}^{2}}
vC=4gh3{v}_{C}=\sqrt{\dfrac{4gh}{3}}
vRvC=32\dfrac{{v}_{R}}{{v}_{C}}=\dfrac{\sqrt{3}}{2}

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