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5.work,energy,power and collision — Physics STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 SciencePhysics5.work,energy,power and collision1 Mark
MCQ
In a vertical circle of radius $r$, at what point in its path a particle has tension equal to zero if it is just able to complete the vertical circle
  • ✓
    Highest point
  • B
    Lowest point
  • C
    Any point
  • D
    At a point horizontally from the centre of circle of radius $r$
✓

Answer

Correct option: A.
Highest point
a
(a)  Let the tension in the string at the highest point be $T$ Minimum speed required by the particle at the highest point to complete the vertical circular motion is $\sqrt{g r}$

$\therefore \quad \frac{m v^{2}}{r}=T+m g$

OR $\quad \frac{m(g r)}{r}=T+m g \quad \Longrightarrow T=0$

Thus tension can be zero at the highest point.

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