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question_answer1) A whistle sends out 256 waves in a second. If the whistle approached the observer with velocity 1/3 of the velocity of sound in air. Find the number of waves per second the observer.
question_answer2) The apparent frequency of a note, when a listener moves towards a stationary source, with velocity of 40 m/s is 200 Hz. When he moves away from the same source with the same speed, the apparent frequency of the same note is 160 Hz. Find the velocity of sound in air. (in m/s)
question_answer3) When an engine passes near to a stationary observer then its apparent frequencies occurs in the ratio 5/3. Find the velocity (in m/s) of engine.
question_answer4) The difference between the apartment frequency of a sound source as perceived by a stationary observer during its approach and recession is 2% of the actual frequency of the source. Find the speed (in m/s) of source. (Speed of sound\[=300m/s\])
question_answer5) A source at rest sends sound waves of constant wavelength. A wall moves towards the source with a velocity of 33 cm/s. The velocity of sound in the medium is 330 m/s. What is the percentage change in wavelength of sound after reflection from the wall.
question_answer6) A source is moving with constant speed\[{{v}_{s}}=20m/sec\]towards a stationary observer due east of source. Wind is blowing at the speed of 20 m/sec due to \[60{}^\circ \]north of east. The source is generating of frequency 500 Hz. Then find frequency (in Hz) registered by observer. [Speed of sound I still air\[=330m/sec.\]]
question_answer7) The apparent frequency of sound heard by a listener is 10% more than the actual frequency of the note emitted by the source when the source moves towards the stationary listener with velocity v. When the source moves with a velocity 2v, the apparent frequency will be more than the actual frequency by (in %)?
question_answer8) A jet fighter flies in a straight line over an airfield line over and airfield with a speed 264 m/s level with the ground, at a height of 600 m. If it emits a continuous note of frequency 1 kHz, what is the change in apparent frequency (in Hz) as experienced by one of the ground crew over a 1.5 s interval as the jet flies overhead? (Assume speed of sound is\[340m{{s}^{-1}}\])
question_answer9) A police van moving with velocity 22 m/s and emitting sound of frequency 176 Hz, follows a motor cycle in turn is moving towards a stationary car and away from the police van. The stationary car is emitting frequency 165 Hz. If motorcyclist does not hear any beats then find his velocity (in m/s) is\[({{v}_{s}}=330m/s)\]
question_answer10) Microwaves which travel with the speed of light are reflected from a distant aeroplane approaching the wave source radar. It is found that when the reflected waves are beat against the waves radiated from the source, the beat frequency is 990 Hz. If the microwaves are 0.1 m in wavelength, what is the approaching speed (in m/s) of the aeroplane?
question_answer11) A bullet passes past a person at a speed of\[=220\text{ }m/s\]. Find the fractional change in the frequency of the whistling sound heard by the person as the bullet crosses the person. Speed of sound in air\[=330m/s.\]
question_answer12) A source and a detector move away from each other, each with a speed of 10 m/s with respect to the ground with no wind. If the detector detects a frequency 1950 Hz of the sound coming from the source, what is the original frequency (in Hz) of the source? Speed of sound in air\[=340m/s.\]
question_answer13) A traffic policeman sounds a whistle to stop a car-driver approaching towards him. The car-driver does not stop and takes the plea in court that because of the Doppler shift, the frequency of the whistle reaching him might have gone beyond the audible limit of 20 kHz and he did not hear it. Experiments showed that the whistle emits a sound with frequency close to 16 kHz. Assuming that the claim of the driver is true, how fast was he driving the car? Take the speed of sound in air to be 330 m/s. Is this speed (in km/hr.) practical with today's technology?
question_answer14) A person going away from a factory on his scooter at a speed of 36 km/h listens to the siren of the factory. If the main frequency of the siren is 600 Hz and a wind is blowing along the direction of the scooter at 36 km/h, find the main frequency (in Hz) as heard by the person.
question_answer15) A boy riding on his bike is going towards east at a speed of \[4\sqrt{2}\]m/s. At a certain point he produces a sound pulse of frequency 1650 Hz that travels in air at a speed of 334 m/s. A second boy stands on the ground \[45{}^\circ \]south of east from him. Find the frequency (in Hz) of the pulse as received by the second boy.
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