Q. Time period of a block suspended from the upper plate of a parallel plate capacitor by a spring of stiffness $k$ is $T.$ When block is uncharged. If a charge $q$ is given to the block then, the new time period of oscillation will be
A) $T$
B) $> T$
C) $< T$
D) $\geq T$
Explanation
(a) The forces that act on the block are $qE$ and $mg.$ Since $qE$ and $mg$ are constant forces, the only variable elastic force changes by $kx.$ Where $x$ is the elongation in the spring $\Rightarrow$ unbalanced (restoring) force $= F = - kx$
$\Rightarrow - m\omega^{2}x = - kx \Rightarrow \omega = \sqrt{\frac{k}{M}} = T$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.