As shown in the figure, $S_1$ and $S_2$ are identical springs with spring constant K each. The oscillation frequency of the mass ' $m$ ' is ' $f$ '. If the spring $\mathrm{S}_2$ is removed, the oscillation frequency will become

The volume of a metal sphere increases by $0.33 \%$ when its temperature is raised by $50^{\circ} \mathrm{C}$. The coefficient of linear expansion of the metal is

The amount of work done in blowing a soap bubble such that its diameter increases from 'd' to ' $D$ ' is ( $T=$ surface tension of solution)

In an a.c. circuit, a resistance ' $R$ ' is connected in series with an inductance ' $L$ '. If phase angle between voltage and current is $45^{\circ}$, the value of inductive reactance will be $\left(\tan 45^{\circ}=1\right)$