Chapter 3: Problem 69
We know, \(\mathrm{T}=2 \pi \sqrt{\frac{l}{\mathrm{~g}}}\) The time period of seconds pendulum, \(\mathrm{T}_{1}=2 \mathrm{~s}\) The length of the second pendulum \(\ell_{1}=100 \mathrm{~cm}=1 \mathrm{~m}\) Now, the new length of the pendulum \(\ell_{2}=2 \ell_{1}\) \(\Rightarrow \ell_{2}=200 \mathrm{~cm}=2 \mathrm{~m}\) Let the new time period of the pendulum be \(=\mathrm{T}_{2}\) \(\Rightarrow \mathrm{T} \alpha \sqrt{l}\) \(\Rightarrow \frac{\mathrm{T}_{1}}{\mathrm{~T}_{2}}=\sqrt{\frac{l_{1}}{l_{2}}} \Rightarrow \mathrm{T}_{2}=\mathrm{T}_{1} \sqrt{\frac{l_{2}}{l_{1}}}\) \(\mathrm{T}_{2}=2 \times \sqrt{\frac{2 l_{1}}{l_{1}}}=2 \sqrt{2} \mathrm{~s}\) The time period becomes \(2 \sqrt{2}\) times the original one.