English
Karnataka Board PUCPUC Science Class 11

A Traffic Policeman Standing on a Road Sounds a Whistle Emitting the Main Frequency of 2.00 Khz. What Could Be the Apparent Frequency - Physics

Advertisements
Advertisements

Question

A traffic policeman standing on a road sounds a whistle emitting the main frequency of 2.00 kHz. What could be the apparent frequency heard by a scooter-driver approaching the policeman at a speed of 36.0 km h−1? Speed of sound in air = 340 m s−1.

Sum
Advertisements

Solution

Velocity of sound in air v = 340 ms−1
Velocity of scooter-driver \[v_o\]= 36 kmh−1 =

\[36 \times \frac{5}{18}   =   10   {\text { ms }}^{- 1}\]

Frequency of sound of whistle \[f_o\]= 2 kHz

Apparent frequency \[\left( f \right)\]  heard by the scooter-driver approaching the policeman is given by : 

\[f = \left( \frac{v + v_o}{v} \right) \times  f_o\]

\[f = \left( \frac{340 + 10}{340} \right) \times 2\] 

\[   = \frac{350 \times 2}{340}  \text { kHz }\] 

\[   =   2 . 06 \text{ kHz }\]

shaalaa.com
Wave Motion
  Is there an error in this question or solution?
Chapter 16: Sound Waves - Exercise [Page 356]

APPEARS IN

HC Verma Concepts of Physics Vol. 1 [English] Class 11 and 12
Chapter 16 Sound Waves
Exercise | Q 62 | Page 356

RELATED QUESTIONS

The wavelengths of two sound waves in air are `81/173`m and `81/170`m. They produce 10 beats per second. Calculate the velocity of sound in air


What is the smallest positive phase constant which is equivalent to 7⋅5 π?


When we clap our hands, the sound produced is best described by Here p denotes the change in pressure from the equilibrium value.


A small source of sounds moves on a circle as shown in figure and an observer is sitting at O. Let \[v_1, v_2,    v_3\] be the frequencies heard when the source is at A, B and C respectively.


When you speak to your friend, which of the following parameters have a unique value in the sound produced?


A man stands before a large wall at a distance of 50.0 m and claps his hands at regular intervals. Initially, the interval is large. He gradually reduces the interval and fixes it at a value when the echo of a clap merges every 3 seconds, find the velocity of sound in air.


Find the minimum and maximum wavelengths of sound in water that is in the audible range (20−20000 Hz) for an average human ear. Speed of sound in water = 1450 m s−1.


The equation of a travelling sound wave is y = 6.0 sin (600 t − 1.8 x) where y is measured in 10−5 m, t in second and x in metre. (a) Find the ratio of the displacement amplitude of the particles to the wavelength of the wave. (b) Find the ratio of the velocity amplitude of the particles to the wave speed.


A sound wave frequency 100 Hz is travelling in air. The speed of sound in air is 350 m s−1. (a) By how much is the phase changed at a given point in 2.5 ms? (b) What is the phase difference at a given instant between two points separated by a distance of 10.0 cm along the direction of propagation?


A string, fixed at both ends, vibrates in a resonant mode with a separation of 2⋅0 cm between the consecutive nodes. For the next higher resonant frequency, this separation is reduced to 1⋅6 cm. Find the length of the string.


In a standing wave pattern in a vibrating air column, nodes are formed at a distance of 4.0 cm. If the speed of sound in air is 328 m s−1, what is the frequency of the source?


The fundamental frequency of a closed pipe is 293 Hz when the air in it is a temperature of 20°C. What will be its fundamental frequency when the temperature changes to 22°C?


Show that if the room temperature changes by a small amount from T to T + ∆T, the fundamental frequency of an organ pipe changes from v to v + ∆v, where \[\frac{∆ v}{v} = \frac{1}{2}\frac{∆ T}{T} .\]


A cylindrical tube, open at both ends, has a fundamental frequency v. The tube is dipped vertically in water so that half of its length is inside the water. The new fundamental frequency is


A car moves with a speed of 54 km h−1 towards a cliff. The horn of the car emits sound of frequency 400 Hz at a speed of 335 m s−1. (a) Find the wavelength of the sound emitted by the horn in front of the car. (b) Find the wavelength of the wave reflected from the cliff. (c) What frequency does a person sitting in the car hear for the reflected sound wave? (d) How many beats does he hear in 10 seconds between the sound coming directly from the horn and that coming after the reflection?


For the propagation of longitudinal waves, the medium must have

  1. elasticity
  2. mass
  3. inertia
  4. force of cohesion

During propagation of a plane progressive mechanical wave ______.

  1. all the particles are vibrating in the same phase.
  2. amplitude of all the particles is equal.
  3. particles of the medium executes S.H.M.
  4. wave velocity depends upon the nature of the medium.

In the wave equation

`y = 0.5sin  (2pi)/lambda(400t - x)m`

the velocity of the wave will be ______.


A transverse wave is represented by y = 2sin (ωt - kx) cm. The value of wavelength (in cm) for which the wave velocity becomes equal to the maximum particle velocity, will be ______.


A small speaker delivers 2W of audio output. At what distance from the speaker will one detect 120 dB intensity sound?

[Given reference intensity of sound as 10-12W/m2]


Share
Notifications

Englishहिंदीमराठी


      Forgot password?
Use app×