When an engine passes near a stationary observer,its apparent frequencies occur in the ratio $5/3$. If the velocity of sound is $340 \ m/s$,then the velocity of the engine is .... $m/s$.

What should be the velocity of a sound source moving towards a stationary observer so that the apparent frequency is double the actual frequency? (Velocity of sound is $v$)

An observer moves towards a stationary source of sound, with a speed of one-fifth of the speed of sound. The apparent increase in the frequency heard by the observer is (in $\%$)

With what velocity an observer should move relative to a stationary source so that a sound of triple the frequency of source is heard by an observer?

$A$ stationary observer receives sound from two identical tuning forks, one of which approaches and the other one recedes with the same speed $v$ (much less than the speed of sound). The observer hears $2 \; \text{beats/sec}$. The oscillation frequency of each tuning fork is $\nu_{0} = 1400 \; \text{Hz}$ and the velocity of sound in air is $c = 350 \; \text{m/s}$. The speed of each tuning fork is close to:

$A$ small source of sound moves on a circle as shown in the figure and an observer is standing at $O.$ Let $n_1, n_2$ and $n_3$ be the frequencies heard when the source is at $A, B$ and $C$ respectively. Then