What is the terminal speed of the paratrooper?

• European Sens
In summary, the paratrooper is carrying a siren that emits a 788 Hz audible signal. The microphone on the plane monitors the signal as the paratrooper falls, and the perceived frequency becomes constant at 412 Hz. Using the equation for the doppler effect, the terminal speed of the paratrooper is calculated to be 313.03 m/s.

Homework Statement

A helicopter drops a paratrooper carrying a siren that emits a 788 Hz audible signal. The microphone (reciever) on the plane monitors the signal from the transmitter as the paratrooper falls. Take the speed of sound in air to be 343 m/s and assume the paratroopers always remains below the helicopter. If the perceived frequency becomes constant at 412 Hz, what is the terminal speed of the paratrooper? Answer in units of m/s.

Homework Equations

Not sure... could you guys help me out.

Possibly Speed = wavelength * frequency ??

The Attempt at a Solution

Probably would need an equation first.

Try and use your knowledge of the doppler effect for this.

I don't really know much about it.

f' = f [(v+v1)/(v-v2)]

that's the equation. could you please walk me through this problem.

Ok so the doppler effect is the apparent change in frequency of a wave due to the motion of the source or the observer.
So f' is the observed and f is the frequency of the source.

$$f' = \frac{fv}{v\pm u}$$

where v is the speed of sound and u is the speed of the source or the observer.
If the source is approaching you it is v - u and if it is moving away it is v + u.

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