Advertisements
Advertisements
प्रश्न
A boy riding on a bicycle going at 12 km h−1 towards a vertical wall whistles at his dog on the ground. If the frequency of the whistle is 1600 Hz and the speed of sound in air is 330 m s−1, find (a) the frequency of the whistle as received by the wall (b) the frequency of the reflected whistle as received by the boy.
Advertisements
उत्तर
Given:
Velocity of sound in air v = 330 ms−1
(a) Frequency of whistle \[n_0\]=1600 Hz
Velocity of source vs = 12 km/h =\[12 \times \frac{5}{18} = \frac{10}{3} {\text { ms }}^{- 1}\]
Velocity of an observer \[v_0\] = 0 ms−1
Frequency of whistle received by wall n =?Frequency of sound received by the observer is given by :
\[n = \frac{v + v_0}{v - v_s} \times n_0\]
On substituting the respective values in the above formula, we get :
\[n = \frac{330 + 0}{330 - \frac{10}{3}} \times 1600 = 1616 \text{ Hz }\]
(b) Here,
Velocity of observer \[v_0\] \[\frac{10}{3} {\text { ms }}^{- 1}\]
Velocity of source vs = 0
Frequency of source \[n_0\]= 1616 Hz
Frequency of sound heard by observer is
\[n = \frac{v + v_0}{v + v_s} \times n_0 \]
On substituting the respective values in the above formula, we get :
\[= \frac{330 + \frac{10}{3}}{330 + 0} \times 1616 = 1632 \text{ Hz }\]
APPEARS IN
संबंधित प्रश्न
A wave is represented by an equation \[y = c_1 \sin \left( c_2 x + c_3 t \right)\] In which direction is the wave going? Assume that \[c_1 , c_2\] \[c_3\] are all positive.
The equation \[y = A \sin^2 \left( kx - \omega t \right)\]
represents a wave motion with
If you are walking on the moon, can you hear the sound of stones cracking behind you? Can you hear the sound of your own footsteps?
The voice of a person, who has inhaled helium, has a remarkably high pitch. Explain on the basis of resonant vibration of vocal cord filled with air and with helium.
When we clap our hands, the sound produced is best described by Here p denotes the change in pressure from the equilibrium value.
When two waves with same frequency and constant phase difference interfere,
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.
Two sources of sound S1 and S2 vibrate at same frequency and are in phase. The intensity of sound detected at a point P as shown in the figure is I0. (a) If θ equals 45°, what will be the intensity of sound detected at this point if one of the sources is switched off? (b) What will be the answer of the previous part if θ = 60°?
The separation between a node and the next antinode in a vibrating air column is 25 cm. If the speed of sound in air is 340 m s−1, find the frequency of vibration of the air column.
Consider the situation shown in the figure.The wire which has a mass of 4.00 g oscillates in its second harmonic and sets the air column in the tube into vibrations in its fundamental mode. Assuming that the speed of sound in air is 340 m s−1, find the tension in the wire.
Two electric trains run at the same speed of 72 km h−1 along the same track and in the same direction with separation of 2.4 km between them. The two trains simultaneously sound brief whistles. A person is situated at a perpendicular distance of 500 m from the track and is equidistant from the two trains at the instant of the whistling. If both the whistles were at 500 Hz and the speed of sound in air is 340 m s−1, find the frequencies heard by the person.
A train running at 108 km h−1 towards east whistles at a dominant frequency of 500 Hz. Speed of sound in air is 340 m/s. What frequency will a passenger sitting near the open window hear? (b) What frequency will a person standing near the track hear whom the train has just passed? (c) A wind starts blowing towards east at a speed of 36 km h−1. Calculate the frequencies heard by the passenger in the train and by the person standing near the track.
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?
A source of sound emitting a 1200 Hz note travels along a straight line at a speed of 170 m s−1. A detector is placed at a distance 200 m from the line of motion of the source. (a) Find the frequency of sound receive by the detector at the instant when the source gets closest to it. (b) Find the distance between the source and the detector at the instant in detects the frequency 1200 Hz. Velocity of sound in air = 340 m s−1.
Which of the following statements are true for wave motion?
In an experiment to determine the velocity of sound in air at room temperature using a resonance tube, the first resonance is observed when the air column has a length of 20.0 cm for a tuning fork of frequency 400 Hz is used. The velocity of the sound at room temperature is 336 ms-1. The third resonance is observed when the air column has a length of ______ cm.
In the wave equation
`y = 0.5sin (2pi)/lambda(400t - x)m`
the velocity of the wave 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]
