• # question_answer Natural length of a spring is 60 cm, and its spring constant is 4000 N/m. A mass of 20 kg is hung from it. The extension produced in the spring is, (Take $g=9.8\ m/{{s}^{2}}$) [DCE 2004] A)             4.9 cm B)             0.49 cm C)               9.4 cm D)             0.94 cm

If x is the extension produced in spring.             $F=kx$ Þ $x=\frac{F}{k}$= $\frac{mg}{k}=\frac{20\times 9.8}{4000}=4.9\,cm$