Question 40

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Jambmaths question: 

The length L of a simple pendulum varies directly as the square of its period T. If a pendulum with period 4 sec. is 64cm.long, find the length of a pendulum whose period is 9sec.

Option A: 

96cm

Option B: 

324cm

Option C: 

36cm

Option D: 

144cm

Jamb Maths Solution: 

$\begin{align}  & L\propto {{T}^{2}} \\ & L=k{{T}^{2}} \\ & \text{when }T=4,\text{ }L=64 \\ & 64=k{{(4)}^{2}} \\ & k=\frac{64}{16}=4 \\ & \text{When }T=9,\text{ }L=? \\ & L=4{{(9)}^{2}}=324cm \\\end{align}$

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