[tex]T=2 \ s \\ \vec{g}=9,8 \ m/s^2 \\ T=2\pi \sqrt{\frac{l}{\vec{g}}} \ \Rightarrow \sqrt{\frac{l}{\vec{g}}}=\frac{T}{2\pi} \\ \Rightarrow \frac{l}{9,8 \ m/s^2}=(\frac{2 \ s}{2 \pi})^2=\frac{1 \ s^2}{\pi^2} \\ \Rightarrow l=9,8 \ m/s^2 \cdot \frac{1 \ s^2}{\pi^2}=\frac{9,8 \ m}{9,8} \\ \Rightarrow \boxed{l=1\ m}[/tex]
