Question

Two small spheres each of mass $m$ and charge $q$ are tied from the same rigid support with the help of silk threads of length $L$ . They make angle $\theta$ with the vertical as shown in the figure. If length $L$ is decreased, then angle $\theta$ with the vertical

• A. increases
• B. decreases
• C. unaffected
• D. cannot say

Answer 1

Answer: (A)

Let tension in the string is $T$ . Then $Tcos\theta =mg$ & $Tsin\theta =\frac{k{q}^2}{{\left(Lsin\theta \right)}^2}$
When length is decreased, distance between two charges decreases and so, the force of repulsion increases. So for equilibrium, $\theta$ also increases.