The Doppler Effect Video Lessons

Concept

# Problem: Two eagles fly directly toward one another, the first at 15.0 m/s and the second at 20 m/s. Both screech, the first one emitting a frequency of 3200 Hz and the second emitting a frequency of 3800 Hz. What frequencies do they receive if the speed of sound is 330 m/s?

###### FREE Expert Solution

Change in frequency as heard by an observer is given by the formula

$\overline{){{\mathbf{f}}}_{\mathbf{o}\mathbf{b}\mathbf{s}\mathbf{e}\mathbf{r}\mathbf{v}\mathbf{e}\mathbf{r}}{\mathbf{=}}{{\mathbf{f}}}_{\mathbf{s}\mathbf{o}\mathbf{u}\mathbf{r}\mathbf{c}\mathbf{e}}{\mathbf{\left(}}\frac{{\mathbf{v}}_{\mathbf{w}\mathbf{a}\mathbf{v}\mathbf{e}}\mathbf{±}{\mathbf{v}}_{\mathbf{o}\mathbf{b}\mathbf{s}\mathbf{e}\mathbf{r}\mathbf{v}\mathbf{e}\mathbf{r}}}{{\mathbf{v}}_{\mathbf{w}\mathbf{a}\mathbf{v}\mathbf{e}}\mathbf{±}{\mathbf{v}}_{\mathbf{s}\mathbf{o}\mathbf{u}\mathbf{r}\mathbf{c}\mathbf{e}}}{\mathbf{\right)}}}$

The wave and the observer move in the same direction so that the numerator becomes

(vwave + vobserver)

The observer and the source move in opposite directions. Thus the denominator becomes

(vwave - vsource)

For the first eagle (observer):

###### Problem Details

Two eagles fly directly toward one another, the first at 15.0 m/s and the second at 20 m/s. Both screech, the first one emitting a frequency of 3200 Hz and the second emitting a frequency of 3800 Hz. What frequencies do they receive if the speed of sound is 330 m/s?