Physics · UNITS AND MEASUREMENT

A simple pendulum has a bob of mass \( m \) attached to a string of length \( l \), oscillating under acceleration due to gravity \( g \). Its time period is given by \( T = 2\pi \sqrt{\frac{l}{g}} \). If the length of the pendulum is increased by \( 21\% \) while keeping mass \( m \) and acceleration due to gravity \( g \) unchanged, the percentage increase in its time period \( T \) will be:

1. A
   10%
2. B
   21%
3. C
   10.5%
4. D
   42%