\(T=2\pi\sqrt{\frac{m}{k}}\)
\(\frac{T'}{T}=\sqrt{\frac{m'}{m}}=\frac{1}{2}\\ \Rightarrow m'=\frac{m}{4}=100g\)
\(T=2\pi.\sqrt{\frac{m}{k}}\)
\(2=2\pi.\sqrt{\frac{0,4}{k}}\Rightarrow k=0,4.\pi^2\)
\(1=2\pi.\sqrt{\frac{m}{k}}=2\pi.\sqrt{\frac{m}{0,4.\pi^2}}\)
\(\Rightarrow m=0,1\left(kg\right)\)