• # question_answer 40) A spring of force constant 800 N/m has an extension of 5 cm. The work done in extending it from 5 cm to 15 cm is A) 16 J                B) 8 J                  C)      32 J                D)      24 J

$\Delta W=\frac{1}{2}k(x_{2}^{2}-x_{1}^{2})=\frac{1}{2}\times 800({{15}^{2}}-{{5}^{2}})\times {{10}^{-4}}=8J$Hence, the correction option is (b).