[tex]m=250 g=0,25 kg\\\Delta E_c=L\\L=L_G+L_N+L_F_{el}\\L_G=0\\L_N=0\\v=0\\L_{el}=-\frac{kx^2}{2}\\ \Delta E_c=E_c-E_c_o=\frac{mv^2}{2}-\frac{mv_o^2}{2}=-\frac{mv_o^2}{2} \\ \Delta E_c=L_{el}<=>-\frac{mv_o^2}{2} =-\frac{kx^2}{2}|(-2)<=>mv_o^2=kx^2=>x=\sqrt{\frac{mv_o^2}{k} }=\sqrt{\frac{0,25*5^2}{50} }=\sqrt{\frac{6,25}{50} }=\sqrt{0,125}=0,35 m\\x=0,35 m[/tex]