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The length L of a simple pendulum varies directly as the square of its period T. If a ...

The length L of a simple pendulum varies directly as the square of its period T. If a pendulum with period 4 sec. is 64 cm long, find the length of pendulum whose period is 9 sec
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  • A 96 cm
  • B 324 cm
  • C 36 cm
  • D 144 cm
Correct Answer: Option B
Explanation:
\(L \propto T^2\)
\(L = kT^2\)
\(k = \frac{L}{T^2}\)
when T = 4, L = 64.
\(k = \frac{64}{4^2} = 4\)
\(L = 4T^2\)
when T = 9,
\(L = 4 \times 9^2 = 324cm\)

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