$SONAR$ emits which of the following waves?

Write Newton's equation for the speed of a sound wave in air.

An engine approaches a hill with a constant speed. When it is at a distance of $0.9 \, km$,it blows a whistle whose echo is heard by the driver after $5 \, s$. If the speed of sound in air is $330 \, m/s$,then the speed of the engine is .... $m/s$.

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: $A$ sound wave has higher speed in solids than gases.
Reason $R$: Gases have higher value of Bulk modulus than solids.
In the light of the above statements,choose the correct answer from the options given below:

$A$ man sets his watch by the sound of a siren placed at a distance of $1 \,km$ away. If the velocity of sound is $330 \,m/s$,what is the status of his watch?

The temperature at which the speed of sound in air becomes double of its value at $27^\circ C$ is ... $^\circ C$