貨運百科

標題:

doppler's effect??

發問:

• 我的jj算不算是短
• QQ AC 如何申請
• 自己一個自由行去新加坡可以嗎--, 請提供行程及那裡可以食煙呢 --@1@

此文章來自奇摩知識+如有不便請留言告知

You are standing on the road. When a car is moving towards you, you hear a frequency of 80Hz. When the car is moving away from you, you hear a frequency of 60Hz. What is the speed of the car? The speed of sound is 343 m/s.

最佳解答:

Since it is the sound soure that is moving, use the Doppler Effect formula, the apparent frequency f is: f = (fo)[c/(c-v)] where fo is the original frequency of sound c is the speed of sound in air v is the speed of the sound source (+ve if moving towards the observor, and -ve if moving away from the oberveor) Hence, 80 = (fo)[343/(343-v)] and 60 = (fo)[343/(343+v)] Dividing, 80/60 = (343+v)/(343-v) i.e. v = 49 m/s

其他解答: