A small source of sound vibrating at frequency 500 Hz is rotated in a circle of radius 100/π cm at a constant angular speed of 5.0 revolutions per second. A listener situates himself in the plane of the circle. Find the minimum and the maximum frequency of the sound observed. Speed of sound in air = 332 m s^-1.

Two identical tuning forks vibrating at the same frequency 256 Hz are kept fixed at some distance apart. A listener runs between the forks at a speed of 3.0 m/s so that he approaches one tuning fork and recedes from the other (figure 16-E10). Find the beat frequency observed by the listener. Speed of sound in air = 332 m/s.

Figure (16-E11) shows a person standing somewhere in between two identical tuning forks, each vibrating at

512 Hz. If both the tuning forks move towards right at a speed of 5.5 m s^-1, find the number of beats heard by the listener. Speed of sound in air = 330 m s^-1.

Two trains are travelling towards each other both at a speed of 90 km h^-1. If one of the trains sounds a whistle at 500 Hz, what will be the apparent frequency heard in the other train? Speed of sound in air = 350 m s^-1.

A traffic policeman sounds a whistle to atop a car-driver approaching towards him. The car-driver does not stop and Lakes 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^-1. Is this speed practical with today’s technology?