Change in frequency when the source is approaching:

$\overline{){{\mathbf{f}}}_{{\mathbf{0}}}{\mathbf{=}}\frac{\mathbf{v}}{\mathbf{v}\mathbf{}\mathbf{-}\mathbf{}{\mathbf{v}}_{\mathbf{s}}}{{\mathbf{f}}}_{{\mathbf{s}}}}$

**(a)**

A student knows that an ambulance siren has a frequency of f_{s} = 399 Hz. He measures, when the ambulance is approaching him. The frequency f_{o} = 414 Hz. Assume the speed of sound is v = 343 m/s in this problem.

(a) Input an expression for the ambulance's speed, v_{s}, in terms of the frequencies and the speed of sound v

(b) What is this speed, in meters per second?

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