Q. The bob of a pendulum of length $l$ is pulled aside from its equilibrium position through an angle $\theta$ and then released. The bob will then pass through its equilibrium position with a speed $v,$ where $v$ equals

A) $\sqrt{2gl(1 - \cos{\theta)}}$
B) $\sqrt{2gl(1 + \sin\theta})$
C) $\sqrt{2gl(1 - \sin\theta})$
D) $\sqrt{2gl(1 + \cos\theta})$
Explanation

(a) When the bob of pendulum is brought to a position making an angle $\theta$ with the equilibrium position, then height of fall of pendulum will be,
$h = l - l\cos\theta = l(1 - \cos\theta)$.
Taking free fall of the
$u = 0,\ a = g,\ g = h = l\left( 1 - \cos\theta \right),\ v = ?$
Now, $v^{2} = u^{2} + 2gh = 0 + 2gl\left( 1 - \cos\theta \right)$
or $v = \sqrt{2gl(1 - \cos\theta)}$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.

Want more practice?
Practice Oscillations MCQs