In an experiment with a beam balance,an unknown mass $m$ is balanced by two known masses of $16\,kg$ and $4\,kg$ as shown in the figure. The value of the unknown mass $m$ is ......... $kg$.

What is the correct order of occurrence ($\%$ by weight) in air of $Ne, Ar$ and $Kr$?

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$A$ lead bullet at $27\,^{\circ}C$ just melts when stopped by an obstacle. Assuming that $25\%$ of the heat is absorbed by the obstacle,the velocity of the bullet at the time of striking is ........ $m/s$. (Melting point of lead $= 327\,^{\circ}C$,specific heat of lead $= 0.03\,cal/g\,^{\circ}C$,latent heat of fusion of lead $= 6\,cal/g$,and $J = 4.2\,J/cal$)

$A$ salt $MX$ has $K_{sp} = 4 \times 10^{-10}$. What value of $K_{sp}$ must another salt $MX_3$ have if the molar solubility of the two salts is to be identical?

Apical dominance is caused by