Doppler Effect

A car $P$ travelling at $20 \mathrm{m} {\mathrm{s}}^{-1}$ sounds its horn at a frequency of $400 \mathrm{Hz}$. Another car $Q$ is travelling behind the first car in the same direction with a velocity $40 \mathrm{m} {\mathrm{s}}^{-1}$. The frequency heard by the passenger of the car $Q$ is approximately [Take, velocity of sound $=360 \mathrm{m} {\mathrm{s}}^{-1}$]

A person driving car at a constant speed of $15 \mathrm{m} {\mathrm{s}}^{-1}$ is approaching a vertical wall. The person notices a change of $40 \mathrm{Hz}$ in the frequency of his car’s horn upon reflection from the wall. The frequency of horn is$\mathrm{\_\_\_\_\_\_\_Hz}.$

(Given: Speed of sound: $30 \mathrm{m} {\mathrm{s}}^{-1}$)

A motorcycle's horn is putting out a $3015 \mathrm{Hz}$ sound as it moves eastward towards a stationary observer. A train sounds its horn at $855 \mathrm{Hz}$ as it heads westward away from that same observer. If the observer hears the frequency of train as $850 \mathrm{Hz}$ and the frequency of motorcycle's horn as $3060 \mathrm{Hz}$, what is the speed of the motorcycle relative to the train (in $\mathrm{m} {\mathrm{s}}^{-1}$)? (Use $\mathrm{m} {\mathrm{s}}^{-1}$ as the speed of sound in air.)

Two trains $A$ and$B$ are moving in the same direction with velocities $30 \mathrm{m} {\mathrm{s}}^{-1}$ and $10 \mathrm{m} {\mathrm{s}}^{-1}$ respectively, $B$ is behind from $A$blows a horn of frequency $450 \mathrm{Hz}$. Then the apparent frequency heard by$B$ is 

A train moving at a speed $v_s$ towards a stationary observer on a platform emits sound of frequency $f$ and velocity $v$. Then the apparent frequency heard by him 

A liquid is filled in a large container as shown. A source '$S$' is moving with constant velocity $\frac{3\mathrm{v}}{4}$ in upward direction. A man '$A$' is stationary on the surface of water such that his ear is in the air. Another man '$B$' is moving downward inside the water with constant velocity $\frac{\mathrm{v}}{3}$. Source emits sound of frequency '$f$'. Speed of sound in the air is $v$ and in the liquid is $5\mathrm{v}$. Then:

A source of sound is travelling towards a stationary observer. The frequency of sound heard by the observer is 10% more than the actual frequency. If the speed of sound is v, that of the source is

A source emitting a sound of frequency $f$ is placed at a large distance from an observer. The source starts moving towards the observer with a uniform acceleration $a$. Find the frequency heard by the observer corresponding to the wave emitted just after the source starts. The speed of sound in the medium is $v$

Two trains $A$ and $B$ simultaneously start moving along parallel tracks from s station along same direction. $A$ starts with constant acceleration $2 \mathrm{m} {\mathrm{s}}^{-2}$ from rest, while $B$ with the same acceleration but with initial velocity of $40 \mathrm{m} {\mathrm{s}}^{-1}$. Twenty seconds after the start, passenger of $A$ hears whistle of $B$. If frequency of whistle is $1194 \mathrm{Hz}$ and velocity of sound in air is $322 \mathrm{m} {\mathrm{s}}^{-1}$, calculate frequency observed by the passenger.

What would be the effect if a moving source accelerated toward a stationary observer?

Does acceleration affect Doppler effect?

A supersonic jet plane moves parallel to the ground at speed $v=0.75$ mach ($1\mathrm{mach}=$ speed of sound). The frequency of its engine sound is ${\nu }_0=2\mathrm{kHz}$ and the height of the jat plane is $h=1.5 \mathrm{km}$. At some instant an observer on the ground hears a sound of frequency $\nu =2{\nu }_0$. Velocity of sound wave in the condition of observer $=340 \mathrm{m} {\mathrm{s}}^{-1}$. The instant prior to the instant of hearing when the sound wave received by the observer was emitted by the jet plane is $(0.9+x)$ sec. Find the value of $x$

A source emitting a sound of frequency $300 \mathrm{Hz}$ is fixed on block $A$ while detector is fixed on block $B$ detects the sound. The blocks $A$ and $B$ are simultaneously displaced towards each other through a distance $1 \mathrm{m}$ and then left to vibrate. Velocity of sound in air $340 \mathrm{m} {\mathrm{s}}^{-1}$ and $S_A$ and $S_B$ are identical blocks $A$ and $B$ are also identical. The frequency of vibration of $S_A$ is $2 \mathrm{Hz}$.

A source is moving with a constant speed $u$ on a straight line, emitting a sound of frequency $f_0$. There are three observers $A,B$ and $C$. $A$ is on the track, $B$ is at a perpendicular distance of $d$ from the track and $C$ is at a perpendicular distance of $2d$ from the track as shown in figure. The variation of the observer frequency with respect to angle $\theta$ subtended at $C$ is given below. ( $d$ is very small)

A fixed sound source $\mathrm{S}$, producing a constant frequency sound is kept at a small distance from a large fixed wall. Now a detector is moved parallel to the wall & with constant velocity, starting from the position of the source at $\mathrm{t}=0$. Then,

A wall is moving with velocity $u$ and a source of sound (frequency $f$) moves with velocity $\frac{u}{2}$ in the same direction as shown. Assuming that the sound travels with a speed of $10u$, pick the right option or options.

A source of sound of single frequency $v_0$ flies along a straight line which is at a finite distance from the observer. Then the observer hears

A toy plane has a siren installed on it. The siren has a frequency of $100 \mathrm{Hz}$. The
plane is moving at a velocity of $160 {\mathrm{ms}}^{-1}$ in the horizontal direction. Assume that vertically upward is y direction, direction of motion of plane is $x$ direction and plane is $8 \mathrm{m}$ above the ground. The origin is vertically below the plane on the ground at a particular instant. Speed of sound $=320 {\mathrm{ms}}^{-1}$. Each of the given options refer to the sound received by recorder corresponding to sound emitted by source at the above mentioned instant when it is above the origin

A radar operates at wavelength $50.0 \mathrm{cm}$. If the beat frequency between the transmitted signal and the signal reflected from aircraft $\left(∆\nu \right)$ is $1 \mathrm{kHz}$, then velocity(in $\mathrm{km} {\mathrm{h}}^{-1}$) of the aircraft will be

A police car moving at $30 \mathrm{m} {\mathrm{s}}^{-1}$, chases a motorcyclist. The policeman sounds his horn at $180 \mathrm{Hz}$, while both of them move towards a stationary siren of frequency $160 \mathrm{Hz}$. The speed (in $\mathrm{m} {\mathrm{s}}^{-1}$) of the motorcyclist to the nearest integer, if it is given that he does not observe any beats is $\alpha$. Write the value of $\left[\alpha \right],$ where $\alpha$ is the greatest integer function.

(Take, the speed of sound $=330 \mathrm{m} {\mathrm{s}}^{-1}$ ).