Chronology | Current Month | Current Thread | Current Date |
[Year List] [Month List (current year)] | [Date Index] [Thread Index] | [Thread Prev] [Thread Next] | [Date Prev] [Date Next] |
[Original Message]
From: Peter Schoch <pschoch@NAC.NET>
To: <PHYS-L@lists.nau.edu>
Date: 3/13/2003 10:48:47 AM
Subject: Doppler Effect Problem
I have a question regarding the Doppler Effect. The following is the
problem I'm trying to 'do':
A car is chasing a UFO through still air. The car is traveling at 30
m/s toward the UFO, while the UFO is traveling at 100 m/s away from the
car. The aliens are playing a note at 330 Hz. What frequency do you,
in the car, hear?
Now, I worked this as f_heard = f_emit (v_air + 30)/(v_air + 100) and I
get an answer, assuming v_air = 343.
However, I _thougth_ that I could also work this as the car being
stationary and the UFO traveling away at 70 m/s using
f_heard = f_emit (v_air) /( v_air + 70), again using v_air = 343. But,
I don't get the same answer.
What am I doing wrong; or more likely, what assumption have I made in
the second case that is wrong?
Thank you,
Peter Schoch
SCCC