A motor cyclist has to rotate in horizontal circles inside the cylindrical wall of inner radius ' $R$ ' metre. If the coefficient of friction between the wall and the tyres is ' $\mu_{\mathrm{s}}$ ', then the minimum speed required is ( $\mathrm{g}=$ acceleration due to gravity)

Two sound waves travelling in the same direction have displacement $\mathrm{y}_1=\mathrm{a} \sin (0.2 \pi \mathrm{x}-50 \pi \mathrm{t})$ and $\mathrm{y}_2=\mathrm{a} \sin (0.15 \pi \mathrm{x}-46 \pi \mathrm{t})$.

How many times, a listener can hear sound of maximum intensity in one second?

Two identical coils of inductance $L$ joined in series are placed very close to each other such that the winding direction of one coil is exactly opposite to that of the other. The net inductance is

The energy needed for breaking a liquid drop of radius ' $R$ ' into 216 droplets, each of radius ' $r$ ' is ' $x$ ' times $T R^2$. The value of ' $x$ ' is [ $T=$ surface tension of the liquid].