Question

If the length of a pendulum is made $9$ times and mass of bob is made $4$ times, then the value of time period becomes

• A. 3 T
• B. 3/2 T
• C. 4 T
• D. 2 T

Answer 1

Answer: (A)

The periodic-time of a simple pendulum is given by
$T=2\pi \sqrt{\frac{l}{g}}$
$T_1=T,l_1=l,l_2=9l$
$\frac{T_1}{T_2}=\sqrt{\frac{l_1}{l_2}}=\sqrt{\frac{1}{9}}=\frac{1}{3}$
$T_2=3T_1=3T$