問題詳情
83. When a rocket is traveling toward a mountain at 100 m/s, the sound waves from thisrocket's engine approach the mountain at speed of V. If the rocket doubles its speed to200 m/s, the sound waves from the engine will now approach the mountain at speedof_________ .
(A) 4V.
(B) 2V.
(C) V.
(D) V.
參考答案