Viteza finala este 0,v=0,deoarece bila se oprese.
Transformam unitatile in SI:m=200 g=0,2 kg
Aplicam teorema de variatie a energiei cintetice intre punctul in care corpul loveste resortul si punctul unde bila se opreste
[tex]\Delta E_c=L\\L=L_G+L_N+L_{F_{el}}\\L_{F_{el}}=-\frac{kx^2}{2}\\ L_N=0\\L_G=0\\\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<=>-\frac{mv_o^2}{2}=-\frac{kx^2}{2}|*(-2)<=>mv_o^2=kx^2=>x^2=\frac{mv_o^2}{k}=>x=\sqrt{\frac{mv_o^2}{k}}=\sqrt{\frac{0,2*4^2}{800} }=\sqrt{0,004}=0,06324 m=6,324 cm\\x=6,324 cm[/tex]
