A train moving at a speed of 220 , ms^ -1 towards a stationary ob… - Vidyadip

MCQ

A train moving at a speed of $220\, ms^{-1}$ towards a stationary object, emits a sound of frequency $1000\, Hz$. Some of the sound reaching the object gets reflected back to the train as echo. The frequency of the echo as detected by the driver of the train is .... $ Hz$ (speed of sound in air is $330\, ms^{-1}$)

A
$3500$
B
$4000$
✓
$5000$
D
$3000$

✓

Answer

Correct option: C.

$5000$

c
Frequency of the echo detected by the driver of the train is

(According to Doppler effect in sound)

$f^{\prime}=\left(\frac{v+u}{v-u}\right) f$

where $f=$ original frequency of source of sound

$f^{\prime}=$ Apparent frequency of source because of the relative motion between source and observer.

$f^{\prime}=\left(\frac{330+220}{330-220}\right) 1000=5000 \mathrm{Hz}$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "M.C.Q (1 Marks)" from 14. waves and sound→14. waves and sound — all question types→Physics STD 11 Science question papers→Gujarat Board STD 11 Science question papers→Gujarat Board question paper generator→

Similar questions

For a train engine moving with speed of $20 \;ms ^{-1}$. the driver must apply brakes at a distance of $500 \;m$ before the station for the train to come to rest at the station. If the brakes were applied at half of this distance, the train engine would cross the station with speed $\sqrt{ x }\; ms ^{-1}$. The value of $x$ is $..............$ (Assuming same retardation is produced by brakes)

Bernoulli's principle is related to:

A particle of mass $10\, gm$ is describing $S.H.M.$ along a straight line with period of $2\, sec$ and amplitude of $10, cm$. Its kinetic energy when it is at $5 \,cm$ from its equilibrium position is

Which of the following quantity is expressed as force per unit area

$Assertion : $ Machine parts are jammed in winter.
$Reason :$ The viscosity of lubricant used in machine parts increase at low temperatures.

Two bullets are fired horizontally and simultaneously towards each other from roof tops of two buldings $100 \;\mathrm{m}$ apart and of same helght of $200 \;\mathrm{m}$ with the same velocity of $25\; \mathrm{m} / \mathrm{s}$. When and where will the two bullets collide. $\left(g=10 \;\mathrm{m} / \mathrm{s}^{2}\right)$

A glass capillary tube is of the shape of a truncated cone with an apex angle $\alpha$ so that its two ends have cross sections of different radii. When dipped in water vertically, water rises in it to a height $h$, where the radius of its cross section is $b$. If the surface tension of water is $S$, its density is $\rho$, and its contact angle with glass is $\theta$, the value of $h$ will be ( $g$ is the acceleration due to gravity)

The string of pendulum of length $l$ is displaced through ${90^o}$ from the vertical and released. Then the minimum strength of the string in order to withstand the tension, as the pendulum passes through the mean position is

The cylindrical tube of a spray pump has radius $R,$ one end of which has $n$ fine holes, each of radius $r.$ If the speed of the liquid in the tube is $v,$ the speed of the ejection of the liquid through the holes is

In a two dimensional motion, instantaneous speed $\text{v}_0$ is a positive constant. Then which of the following are necessarily true?