1/ \(2A=6\Rightarrow A=3\left(cm\right)\)
\(f=6\left(Hz\right)\Rightarrow\omega=12\pi\left(rad/s\right)\)
\(\Rightarrow v_{max}=\omega A=3.12\pi=36\pi\left(cm/s\right)\)
2/ \(T=2\pi\sqrt{\frac{l}{g}}\Rightarrow l=\frac{1,63^2.10}{4.10}=....\left(cm\right)\)