Question

A simple pendulum of length $81cm$ takes $3$ minutes to execute $100$ oscillations. The time that a simple pendulum of length $121cm$ takes to make the same number of oscillations is

• A. $2minute$
• B. $3.66minute$
• C. $4.2minute$
• D. $4.67minute$

Answer 1

Answer: (B)

$3.66minute$

$T=2\pi \sqrt{\frac{81}{g}}$
$T^1=2\pi \sqrt{\frac{121}{g}}$
$T^1=\frac{11}{9}T$
$\therefore$ for 100 oscillation , time taken is
$\therefore T^1=\frac{3\times 11}{9}$
$=3.66min$