Chapter 5 - Work and Energy - Learning Path Questions and Exercises - Exercises - Page 175: 21

a). (1) $\sqrt 2$ b). $900J$

a). $W^{'}=2W=2\times\frac{1}{2}kx^{2}=\frac{1}{2}k(\sqrt 2x)^{2}$ So, if twice the amount of work is done, the stretch increase by factor of $\sqrt 2$. b). $100J=\frac{1}{2}\times k\times 0.01^{2}$ Now, $W^{'}=\frac{1}{2}\times k \times 0.03^{2}$ From above 2 equations, $W^{'}=9\times100=900J$