A particle having a charge of

Question:

A particle having a charge of $\times 10^{-4} \mathrm{C}$ is placed directly below and at a separation of $10 \mathrm{~cm}$ from the bob of a simple pendulum at rest. The mass of the bob is $100 \mathrm{~g}$, what charge should the bob be given so that the string becomes loose.

Solution: