The binding energy for the following nuclear reactions are expressed in MeV .

$$ \begin{aligned} & { }_2 \mathrm{He}^3+{ }_0 \mathrm{n}^1 \rightarrow{ }_2 \mathrm{He}^4+20 \mathrm{MeV} \\ & { }_2 \mathrm{He}^4+{ }_0 \mathrm{n}^1 \rightarrow{ }_2 \mathrm{He}^5-0.9 \mathrm{MeV} \end{aligned} $$

If $\mathrm{X}_3, \mathrm{X}_4, \mathrm{X}_5$ denote the stability of ${ }_2 \mathrm{He}^3,{ }_2 \mathrm{He}^4$ and ${ }_2 \mathrm{He}^5$, respectively, then the correct order is :

A thin uniform rod $(X)$ of mass $M$ and length $L$ is pivoted at a height $\left(\frac{L}{3}\right)$ as shown in the figure. The rod is allowed to fall from a vertical position and lie horizontally on the table. The angular velocity of this rod when it hits the table top, is $\_\_\_\_$ .

( $\mathrm{g}=$ gravitational acceleration)

A point source is kept at the center of a spherically enclosed detector. If the volume of the detector increased by 8 times, the intensity will

A regular hexagon is formed by six wires each of resistance $r \Omega$ and the corners are joined to the centre by wires of same resistance. If the current enters at one corner and leaves at the opposite corner, the equivalent resistance of the hexagon between the two opposite corners will be