Which of the following alcohols reacts most rapidly with alkali metals?

$A$ progressive wave of frequency $50 ~Hz$ is travelling with velocity $350 ~m/s$ through a medium. The change in phase at a given time interval of $0.01 ~s$ is

In the circuit shown,the current in the $1\,\Omega$ resistor is

The average kinetic energy of a gas molecule at $27\,^{\circ}C$ is $6.21 \times 10^{-21}\,J$. Its average kinetic energy at $227\,^{\circ}C$ will be

$A$ block placed on a rough inclined plane of inclination $\theta=30^{\circ}$ can just be pushed upwards by applying a force $F$ as shown. If the angle of inclination of the inclined plane is increased to $\theta=60^{\circ}$,the same block can just be prevented from sliding down by application of a force of the same magnitude $F$. The coefficient of friction between the block and the inclined plane is:

Which of the following substances does not contain a $-COOH$ group?