A solid cylinder of radius 'R' and mass 'M' rolls down an inclined plane of height 'h'. When it reaches the…

A solid cylinder of radius 'R' and mass 'M' rolls down an inclined plane of height 'h'. When it reaches the bottom of the plane, its rotational kinetic energy is $(\mathrm{g}=$ acceleration due to gravity)
  1. $\frac{\text { Mgh }}{3}$
  2. Mgh
  3. $\frac{\text { Mgh }}{2}$
  4. $\frac{\mathrm{Mgh}}{4}$

Solution

$\begin{aligned} \text { Total } \mathrm{KE} &=\frac{1}{2} \mathrm{Mv}^{2}+\frac{1}{2} \mathrm{I} \omega^{2} \\ &=\frac{1}{2} \mathrm{Mv}^{2}+\frac{1}{2}\left(\frac{1}{2} \mathrm{MR}^{2}\right) \mathrm{v}^{2} \\ &=\frac{1}{2} \mathrm{Mv}^{2}+\frac{1}{4} \mathrm{Mv}^{2}=\frac{3}{4} \mathrm{Mv}^{2}=\mathrm{Mgh} \end{aligned}$

Asked in: MHT CET 2020 (16 Oct Shift 1)

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