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An observer is standing stationary in air moving at a speed of 2m/s. A source of frequency 20Hz is moving in the direction of wind with speed 10m/s towards the observer. What will be the frequency as heard by the observer? Speed of sound in air is 330m/s.

Correct Answer: 20.62Hz
As the air is moving, we can solve this question from the air’s frame of reference. From the air’s frame of reference, the observer will be going towards the observer at 2m/s and the source will be coming towards the observer at 10-2 = 8m/s. F = f(v+v0)/(v+v8) = 20(330+2)/(330-8) = 20*332/322 = 20.62Hz.

A source of frequency 50Hz is moving towards an observer with a deceleration of 2m/s2. If its initial speed is 20m/s, what will be the maximum frequency heard by the observer? Initial distance between source and observer is 100m. Speed of sound = 330m/s.

A source moves towards a stationary observer with a speed of 10m/s. If the frequency of the source is 10Hz what will be the wavelength of sound heard by the observer? Speed of sound = 330m/s.

A man is moving towards a wall with a source of sound in his hand. Frequency of source = 50Hz. Speed of man = 8m/s. If the man sends one pulse of sound, what will be the frequency heard by him after sound reflects off the wall? Speed of sound = 330m/s.

A source of sound frequency 600Hz is placed inside water. The speed of sound in water is 1500 m/s and in air it is 300 m/s. The frequency of sound is recorded by an observer, who is standing in the air is?

The source of sound generating of a frequency of 3 kHz reaches an observer with a speed of 0.5 times the velocity of sound in air. The frequency heard by the observer is?

A train moves towards a stationary observer with speed 34m/s. The train sounds a whistle and its frequency registered by the observer is f1. If the train’s speed is reduced to 17m/s, the frequency registered is f2. If the speed of sound is 340m/s, then the ratio f1/f2 is?

A whistle giving out 450Hz approaches a stationary observer at a speed of 33m/s. The frequency heard by the observer in Hz is (speed of sound = 330m/s).

A vehicle, with a horn of frequency n is moving with a velocity of 30m/s in a direction perpendicular to the straight line joining the observer and the vehicle. The observer perceives the sound to have a frequency n+n1. Then (if the sound velocity in air is 300m/s)

An observer standing by the side of a road hears the siren of an ambulance, which is moving away from him. If the actual frequency of the siren is 2000Hz, then the frequency heard by the observer will be __________

In a class, seven students are standing in a row. Q is standing left to R but right to P. O is standing right to N and left to P. Similarly, S is standing right to R and left to T. Find out who is standing in the middle ?