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STD 11 - 6. system of particles and rotational motion — JEE STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceJEESTD 11 - 6. system of particles and rotational motion4 Marks
MCQ
A smooth sphere $A$ is moving on a frictionless horizontal plane with angular speed $\omega $ and center of mass with velocity $v$. It collides elastically and head-on with an identical sphere $B$ at rest. Neglect friction everywhere. After the collision, their angular speeds are ${\omega _A}$ and ${\omega _B}$ respectively. Then
  • A
    ${\omega _A} < {\omega _B}$
  • B
    ${\omega _A} = {\omega _B}$
  • ✓
    ${\omega _A} = \omega $
  • D
    $\omega = {\omega _B}$
✓

Answer

Correct option: C.
${\omega _A} = \omega $
c
As the spheres are smooth there will be no friction (no torque) and therefore there will be no transfer of angular momentum. Thus $\mathrm{A}$, after collision will remain with its intial angular momentum $i . e ., \omega_{A}=\omega$

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