Question

An object producing a sound of frequency 400 Hz approaches a stationary person with a speed of 200 ms–1. The speed of sound is 300 ms–1. As the object flies past him, the person will note a change in frequency of  

Solution

Correct option is

960 Hz

 

Given, us = 200 ms–1v = 300 ms–1 and V = 400 Hz. The apparent frequency when the source of sound approaches the stationary observer is given by 

                            

The apparent frequency when the source flies past him is

                             

  

                                                         

                                                         

                                                       

SIMILAR QUESTIONS

Q1

A tuning fork produces 4 beats per second when sounded with a sonometer of vibrating length 48 cm. It produces 4 beats per second also when the vibrating length is 50 cm. What is the frequency of the tuning fork?

Q2

Two identical strings of a stringed musical instrument are in unison when stretched with the same tension. When the tension in one string is increased by 1%, the musician hears 4 beats per second. What was the frequency of the note when the strings were in unison?

Q3

Two identical flutes produce fundamental notes of frequency 300 Hz at 27oC. If the temperature of the air in one flute is increased to 31oC, the number of beats heard per second will be

Q4

The wavelength of light of a particular wavelength received from a galaxy is measured on earth and is found to be 5% more that its wavelength. It follows that the galaxy is

Q5

Radio waves of frequency 600 MHz are sent by a radar towards an enemy aircraft. The frequency of the radio waves reflected from the aircraft as measured at the radar station is found to increase by 6 kHz. It follows that the aircraft is

Q6

Three waves of equal frequency having amplitude 10 μm, 4 μm and 7μ arrive at a given point with a successive phase difference of π/2. The amplitude of the resulting wave in μ m is given by

Q7

Two wires of the same material and radii r and 2r are welded together end to end. The combination is used as a sonometer wire and kept under tension T. The welded point is mid-way between the two bridges. When stationary waves are set up in the composite wire, the joint is a node. Then the ratio of the number of loops formed in the thinner to thicker wire is

Q8

A uniform rope of length 12m and mass 6 kg hangs vertically from a rigid support. A block of mass 2 kg is attached to the free end of the rope. A transverse pulse of wavelength 0.06 m is produced in the lower end of the rope. What is the wavelength of the pulse when it reached the top of the rope?

Q9

A tuning fork and a sonometer wire sounded together produce 4 beats per second when the length of the wire is 95 cm or 100 cm. the frequency of the turning fork is

Q10

 

The frequency of the sound of a car horn as received by an observer towards whom the car is moving differs from the frequency of the horn by 2.5%. If the speed of sound in air is

320 ms–1, the speed of the car is