Posted by **Andrea** on Friday, February 29, 2008 at 11:40am.

The frequency of a stationary siren is 1500 Hz when measured by a stationary observer. If an observer moves away from the siren at mach number .85 what is the frequency he hears? (assume room temperature so that velocity of the air is 340m/s)

I know that I would use f'=f (v - v_o)/(v + v_s)

But what I don't get is the mach number .85

Isn't mach number .85 = v_s/v?

How would I set up this problem?

Should it look like this:

=(1500Hz) (1-0)/(340m/s+.85)

=4.4Hz

Is this correct?

## Answer This Question

## Related Questions

- physics - A police car, whose siren has a natural frequency of 620Hz, moves away...
- Physics - a siren has a frequency of 1099 Hz when it and an observer are both at...
- Physics - An airplane moves away from a stationary observer at 125 m/s and ...
- Physics - Question about doppler effect: How do you solve when it gives you ...
- physics - 1)As a sound source moves away from a stationary observer, the number ...
- physics - An observer detects an apparent frequency of 505 hz coming from a 500 ...
- physics - 1)As a sound source moves away from a stationary observer, the number ...
- phys - An observer detects an apparent frequency of 505 hz coming from a 500 hz...
- Chemistry Physics - What frequency is heard by an observer who hears the 450 Hz ...
- math physics - What frequency is heard by an observer who hears the 450 Hz siren...

More Related Questions