Assignment Problems

ASSIGNMENT PROBLEMS

Note: Use following physical constants wherever required:

speed of sound in air, v = 330 m/s 

speed of light, c = 3 × 108 m/s

1. With what velocity should a sound-source travel towards a stationary observer so that the apparent frequency may be double of this actual frequency?

[Ans. v /2 where v is velocity of sound]

2. With what velocity should a sound source move towards a stationary observer so that the apparent frequency heard be three-times its real frequency.

[Ans. 280 m / s]

3. With what velocity should a moving observer go away from a stationary source so that the apparent frequency heard be half of its real frequency. If observer is stationary and source goes away then?

[Ans. 165 m/s, 330 m/s]

4. A motor-car is approaching towards a crossing with a velocity 75 km/h. The traffic man standing at crossing hears the frequency of sound of horn to be 260 Hz. What is the real frequency of sound of horn? 

[Ans. 244 Hz]