# Homework Help: Airplane & Frequency of Sound

1. Aug 3, 2006

### PhysicsHatesMe01

I've got another one.

An airplane traveling at v = 154 m/s emits a sound of frequency 5.20 kHz. At what frequency does a stationary listener hear the sound during each of the following times? (Use 344 m/s as the speed of sound.)

1) as the plan approaches (kHz)
2) after it passes (kHz)

What equation do I use to solve this?

Basically, I'm at a loss for almost all of my homework problems. My prof goes through the chapters during lecture, but he doesn't do very many examples which is why this class is causing me problems.

-- NVM. I figured it out :)

Last edited: Aug 3, 2006
2. Aug 3, 2006

### Staff: Mentor

Good job. See! Physics loves you!

3. Aug 4, 2006

### sdekivit

For approaching, the formula for the Doppler-effect is different than for passing, since for approaching the frequencty the listener hears is getting higher --> mulitply with $$\frac {v} {v-v_{source}}$$ and when passing the frequence gets lower --> multiply with $$\frac {v} {v + v_{source}}$$