Question

A whistle of frequency 556 Hz moves in a circle of radius 57.6 cm at an angular speed of 16.4 rad/s. What are (a) the lowest and (b) the highest frequencies heard by a listener a long distance away, at rest with respect to the center of the circle? (Take the speed of sound in air to be 343 m/s.)

Answer 1

The linear velocity of the whistle is, v'= ro = (57.6x10-² m) (16.4 rad/s) = 9.45 m/s (a) The lowest frequency by the listener a long distance away, at rest with respect to center of the circle is, (1-1' fiowest = fol 343 m/s -9.45 m/s =(556 Hz) 343 m/s = 540.68 Hz (b) The highest frequency by the listener a long distance away, at rest with respect to center of the circle is, = (556 Hz) 343 m/s +9.45 m/s) 343 m/s = 571.32 Hz