$A$ man fires a bullet standing between two cliffs. The first echo is heard after $3 \, s$ and the second echo is heard after $5 \, s$. If the velocity of sound is $330 \, m/s$,then the distance between the cliffs is .... $m$

$A$ man stands in front of a hillock and fires a gun. He hears an echo after $1.5\, s$. The distance of the hillock from the man is ...... $m$ (velocity of sound in air is $330\, m/s$).

$A$ man sets his watch by a whistle that is $2\, km$ away. How much will his watch be in error? (Speed of sound in air = $330\, m/s$)

At what temperature does the velocity of sound in air increase by $10\%$ compared to its velocity at $0^{\circ}C$ (in $^{\circ}C$)?

$A$ narrow sound pulse (for example,a short pip by a whistle) is sent across a medium.
$(a)$ Does the pulse have a definite $(i)$ frequency,$(ii)$ wavelength,$(iii)$ speed of propagation?
$(b)$ If the pulse rate is $1$ after every $20 \; s$,(that is,the whistle is blown for a split of a second after every $20 \; s$),is the frequency of the note produced by the whistle equal to $1/20$ or $0.05 \; Hz$?

$A$ source $S$ of frequency $f_0$ and an observer $O$,moving with speeds $v_1$ and $v_2$ respectively,are moving away from each other. When they are separated by a distance $a$ at $t = 0$,a pulse is emitted by the source. This pulse is received by $O$ at time $t_1$. Then $t_1$ is equal to: