MCQ
Two pendulums begins to swing simultaneously. The first pendulum makes $11$ full oscillations when the other makes $9$. The ratio of length of the two pendulums is
- A$11/9$
- B$9/11$
- ✓$81/121$
- D$121/84$
✓
Answer
Correct option: C.
$81/121$
c
$11 \times 2 \pi \sqrt{\frac{\ell_{s}}{g}}=9 \times 2 \pi \sqrt{\frac{\ell_{\ell}}{g}}$
$11 \times 2 \pi \sqrt{\frac{\ell_{s}}{g}}=9 \times 2 \pi \sqrt{\frac{\ell_{\ell}}{g}}$
$121 C_{3}=81 \ell_{\ell}$
$\frac{\ell_{s}}{\ell_{\ell}}=\frac{81}{121}$
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