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JEE Main 202125 FebruaryEvening Shift
Exam
JEE Main
Year
2021
Date
25 February
Shift
Evening Shift
Subject
Physics
Chapter
Rotational Motion

JEE Main 2021 · 25 February · Evening Shift · Physics · Rotational Motion

A sphere of radius a and mass m rolls along a horizontal plane with...

A sphere of radius aa and mass mm rolls along a horizontal plane with constant speed v0{v}_{0}. It encounters an inclined plane at angle θ\theta and climbs upward. Assuming that it rolls without slipping, how far up the sphere will travel?

A sphere of radius a and mass m rolls along a horizontal plane with constant speed v _ 0 . It encounters an inclined

Options

  1. A25v02gsinθ\dfrac{2}{5}{v}_{0}^{2}gsin\theta
  2. B7v0210gsinθ\dfrac{7{v}_{0}^{2}}{10gsin\theta}
  3. Cv025gsinθ{v}_{0}^{2}5gsin\theta
  4. Dv022gsinθ{v}_{0}^{2}2gsin\theta

Correct answer

B. 7v0210gsinθ\dfrac{7{v}_{0}^{2}}{10gsin\theta}

Step-by-step solution

A sphere of radius a and mass m rolls along a horizontal plane with constant speed v _ 0 . It encounters an inclined

From energy conservation
mgh=12mv02+12Iω2mgh = \dfrac{1}{2}{mv}_{0}^{2} + \dfrac{1}{2}{I \omega}^{2}
⇒mgh=12mv02+12×25ma2×v02a2⇒ mgh = \dfrac{1}{2}{mv}_{0}^{2} + \dfrac{1}{2} \times \dfrac{2}{5}{ma}^{2} \times {v}_{0}^{2}{a}^{2}
⇒gh=12v02+15v02⇒ gh = \dfrac{1}{2}{v}_{0}^{2} + \dfrac{1}{5}{v}_{0}^{2}
⇒gh=710v02⇒ gh = \dfrac{7}{10}{v}_{0}^{2}

From triangle, sinθ=hlsin\theta = \dfrac{h}{l}
Then h=lsinθh = lsin\theta
⇒lsinθ=710v02g⇒ lsin\theta = \dfrac{7}{10}{v}_{0}^{2}g
Thus, the sphere will travel distance, l=710v02gsinθl = \dfrac{7}{10}\dfrac{{{v}_{0}}^{2}}{gsin\theta}.

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