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JEE Main 202126 FebruaryEvening Shift
Exam
JEE Main
Year
2021
Date
26 February
Shift
Evening Shift
Subject
Physics
Chapter
Rotational Motion

JEE Main 2021 · 26 February · Evening Shift · Physics · Rotational Motion

A cord is wound round the circumference of wheel of radius r , The...

A cord is wound round the circumference of wheel of radius rr, The axis of the wheel is horizontal and the moment of inertia about it is II. A weight mgmg is attached to the cord at the end. The weight falls from rest. After falling through a distance h,h, the square of angular velocity of wheel will beA cord is wound round the circumference of wheel of radius r , The axis of the wheel is horizontal and the moment of

Options

  1. A2mghI+mr2\dfrac{2mgh}{I + m{r}^{2}}
  2. B2mghI+2mr2\dfrac{2mgh}{I + 2m{r}^{2}}
  3. C2gh2gh
  4. D2ghI+mr2\dfrac{2gh}{I + m{r}^{2}}

Correct answer

A. 2mghI+mr2\dfrac{2mgh}{I + m{r}^{2}}

Step-by-step solution

A cord is wound round the circumference of wheel of radius r , The axis of the wheel is horizontal and the moment of

mgh=12Iω2+12mv2mgh = \dfrac{1}{2}I{\omega}^{2} + \dfrac{1}{2}m{v}^{2}

v=\omegarv = \omegar

mgh=12Iω2+12mω2r2mgh = \dfrac{1}{2}I{\omega}^{2} + \dfrac{1}{2}m{\omega}^{2}{r}^{2}

2mgh(I+mr2)=ω2\dfrac{2mgh}{\left(I + m{r}^{2}\right)} = {\omega}^{2}

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