Q: Two spring of spring constants 1500 N/m and 3000 N/m respectively are stretched by the same force. The potential energy gained by the two spring will be in the ratio
Sol: $\large U = \frac{F^2}{2 K}$
if force F is same on two spring
$\large U \propto \frac{1}{K}$
$\large \frac{U_1}{U_2} = \frac{K_2}{K_1}$
$\large \frac{U_1}{U_2} = \frac{3000}{1500} = \frac{2}{1}$