The potential energy of 'a long spring when it is stretched by 3 cm is ' $U$ '. If the spring is stretched…
The potential energy of 'a long spring when it is stretched by 3 cm is ' $U$ '. If the spring is stretched by 9 cm , potential energy stored in it will be
$3 \dot{U}$
$4 U$
5 U
$9 U$
Solution
P.E. stored in spring is, $\mathrm{U}=\frac{1}{2} \mathrm{kx}^2$
$\begin{array}{ll}
\therefore & \frac{U^{\prime}}{U}=\left(\frac{x_2}{x_1}\right)^2=\left(\frac{9}{3}\right)^2=(3)^2=9 \\
\therefore & U^{\prime}=9 U
\end{array}$
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