A parallel beam of light is incident normally on a plane surface absorbing $50 \%$ of the light and reflecting the rest. If the incident beam carries 90 W of power, the force exerted by it on the surface is ( $\mathrm{C}=$ velocity of light in air $=3 \times 10^8 \mathrm{~m} / \mathrm{s}$ )

A tyre of a vehicle is filled with air having pressure 270 kPa at $27^{\circ} \mathrm{C}$. The air pressure in the tyre when the temperature increases to $37^{\circ} \mathrm{C}$ is

A $20 \Omega$ resistance, 10 mH inductance coil and $15 \mu \mathrm{~F}$ capacitor are joined in series. When a suitable frequency alternating current source is joined to this combination, the circuit resonates. If the resistance is made $\frac{1}{3} \mathrm{rd}$, the resonant frequency

If the period of a oscillation of mass ' m ' suspended from a spring is 2 s , then the period of suspended mass ' 4 m ' with the same spring will be