Question

Two tuning forks of frequencies 350 Hz each move relative to a stationary observer. One fork moves away from the observer, while the other moves toward him at the same speed. The observer hears beats of frequency 4 Hz. Find the speed of each tuning fork relative to the stationary observer. Velocity of sound in air = 340 m s^–1.

Answer 1

The apparent frequency of the tuning fork coming towards the stationary observer is

where v_s = speed of the tuning fork. 

The apparent frequency of the tuning fork going away from the observer is

Since v_s is positive, the positive root of the above equation is