Question: (A) An opera singer in a convertible sings a note at 600 Hz whilecruising down the highway at 90\;{\rm km}/{\rm hr}.
(1) What is the frequency heard by a person standing beside the road in front ofthe car?
(2) What is the frequency heard by a person on the ground behind thecar?
(B) A whistle you useto call your hunting dog has a frequency of 21 kHz, but your dog isignoring it. You suspect the whistle may not be working, but youcan't hear sounds above 20 kHz. To test it, you ask a friend toblow the whistle, then you hop on your bicycle.
(1) At what minimumspeed should you ride to know if the whistle isworking?