Two wires of the same material (Young's modulus $=Y$ ) and same length $L$ but radii $R$ and $2 R$ respectively are joined end to end and a weight $w$ is suspended from the combination as shown in the figure. The elastic potential energy in the system is

$\frac{3 w^2 L}{4 \pi R^2 Y}$
$\frac{3 w^2 L}{8 \pi R^2 Y}$
$\frac{5 w^2 L}{8 \pi R^2 Y}$
$\frac{w^2 L}{\pi R^2 Y}$
A pure resistive circuit element $X$, when connected to an AC supply of peak voltage 200 V , gives a peak current of 5 A . A second circuit element $Y$, when connected to the same AC supply also gives the same value of peak current but the current lags behind by $90^{\circ}$. If the series combination of $X$ and $Y$ is connected to the same supply, what will be the rms value of current?
$\frac{10}{\sqrt{2}} \mathrm{~A}$
$\frac{5}{\sqrt{2}} \mathrm{~A}$
$\frac{5}{2} \mathrm{~A}$
5 A
The equivalent resistance of the circuit across $A B$ is given by

$4 \Omega$
$13 \Omega$
$4 \Omega$ or $13 \Omega$
$4 \Omega$ or zero
The fundamental frequency of a closed organ pipe is same as the first overtone frequency of an open organ pipe. If the length of open organ pipe is 50 cm , then the length of closed organ pipe is
25 cm
12.5 cm
100 cm
200 cm
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