A ring and a disc of same mass and same diameter are rolling without slipping. Their linear velocities are…

A ring and a disc of same mass and same diameter are rolling without slipping. Their linear velocities are same, then the ratio of their kinetic energy is
  1. 0.75
  2. 1.33
  3. 0.5
  4. 2.66

Solution

For ring, $\frac{\mathrm{K}^2}{\mathrm{R}^2}=1$ For disc, $\frac{\mathrm{K}^2}{\mathrm{R}^2}=\frac{1}{2}$ $\begin{aligned} & \frac{(\mathrm{K} . \mathrm{E})_{\text {ring }}}{(\mathrm{K} . \mathrm{E})_{\text {disc }}}=\frac{\left[\frac{1}{2} \mathrm{mv}^2\left(1+\frac{\mathrm{K}^2}{\mathrm{R}^2}\right)\right]_{\text {ring }}}{\left[\frac{1}{2} \mathrm{mv}^2\left(1+\frac{\mathrm{K}^2}{\mathrm{R}^2}\right)\right]_{\text {disc }}} \\ & =\frac{(1+1)}{\left(1+\frac{1}{2}\right)}=\frac{2 \times 2}{3}=1.33 \end{aligned}$

Asked in: AP EAMCET 2024 (22 May Shift 2)

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