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

Rajasthan BoardEnglish MediumSTD 11 SciencePhysics5.work,energy,power and collision1 Mark
MCQ
A simple pendulum oscillates in a vertical plane. When it passes through the mean position, the tension in the string is $3$ times the weight of the pendulum bob. What is the maximum displacement of the pendulum of the string with respect to the vertical ......... $^o$.
  • A
    $30$
  • B
    $45$
  • C
    $60$
  • ✓
    $90$
✓

Answer

Correct option: D.
$90$
d
(d) Tension at mean position, $mg + \frac{{m{v^2}}}{r} = 3\,mg$

$v = \sqrt {2gl} $…$(i)$

and if the body displaces by angle  $\theta$ with the vertical then $v = \sqrt {2gl(1 - \cos \theta )} $…$(ii)$

Comparing $(i)$ and $(ii)$, $\cos \theta = 0$

$⇒$ $\theta = 90^\circ $

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