# A long spring is stretched by 3cm and its potential energy is U.If spring is stretched by 12cm,its potential energy will be

$\begin{array}{1 1}(A)\;U/4\\(B)\;U/16\\(C)\;4U\\(D)\;16U\end{array}$

$U \propto (strain)^2$
So $\large\frac{U_2}{U_1}=(\frac{12}{3})^2$
$\Rightarrow 16$
$U_2=16U$
Hence (D) is the correct answer.