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Rotational Mechanics — Physics STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 SciencePhysicsRotational Mechanics1 Mark
MCQ
A uniform rod is kept vertically on a horizontal smooth surface at a point O. If it is rotated slightly and released, it falls down on the horizontal surface. The lower end will remain:
  • A
    At O.
  • B
    At a distance less than $\frac{\text{l}}2{}$ from O.
  • ✓
    At a distance $\frac{\text{l}}2{}$ from O.
  • D
    At a distance larger than $\frac{\text{l}}2{}$ from O.
✓

Answer

Correct option: C.
At a distance $\frac{\text{l}}2{}$ from O.
It is given that there is no force along x-axis.
COM of rod will remain and will not shift along x-axis (horizontal direction).
Force gravity is acting along y-axis (vertical direction). So, COM will shift along the y-axis by $\frac{\text{l}}2{}$ distance and COM of horizontal rod is at a distance $\frac{\text{l}}2{}$ from one end.
Therefore, lower end of the rod will remain at a distance $\frac{\text{l}}2{}$ from O.

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