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NEET 2003
Exam
NEET
Year
2003
Subject
Physics
Chapter
Rotational Motion

NEET 2003 · Physics · Rotational Motion

A solid cylinder of mass M and radius R rolls without slipping on...

A solid cylinder of mass MM and radius RR rolls without slipping on an inclined plane of length LL and height hh. What is the speed of its centre of mass when the cylinder reaches its bottom?

Options

  1. A2gh\sqrt{2 g h}
  2. B34gh\sqrt{\frac{3}{4} g h}
  3. C43gh\sqrt{\frac{4}{3} g h}
  4. D4gh\sqrt{4 g h}

Correct answer

C. 43gh\sqrt{\frac{4}{3} g h}

Step-by-step solution

Here K.E. of centre of mass when cylinder reached the bottom =12mv2+12=\frac{1}{2} m v^2+\frac{1}{2}\mathrm{I}ω2…(i)\omega^2 \ldots(\mathrm{i}) Here I=12MK2\mathrm{I}=\frac{1}{2} M K^2 and ω=VR\omega=\frac{V}{R} ∴KE=12mv2+12MK2⋅V2r2=12mv2[1+K2R2]\begin{aligned} & \therefore \mathrm{KE}=\frac{1}{2} m v^2+\frac{1}{2} M K^2 \cdot \frac{V^2}{r^2} \\ & =\frac{1}{2} m v^2\left[1+\frac{K^2}{R^2}\right] \end{aligned} But for solid cylinder K=R2K=\frac{R}{\sqrt{2}} or K2R2=12\frac{K^2}{R^2}=\frac{1}{2} ∴KE=34mv2\therefore K E=\frac{3}{4} m v^2 PE of the solid cylinder at height hh is PE=mgh\mathrm{PE}=m g h From eq. (ii) and (iii) mgh=34mv2⇒v=43gh\begin{aligned} & m g h=\frac{3}{4} m v^2 \\ & \Rightarrow v=\sqrt{\frac{4}{3} g h} \end{aligned}
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