You are standing still. What frequency do you detect if a fire engine whose siren emits at 1550 Hz move at a speed of 32.0 m/s:

(a) toward you?

(b) away from you?

a)

source moving toward the observer at rest requires the formula: f' = f / (1 - Vsource / Vsnd)

f' = 1550 / (1 - 32 / 343)

f' = 1709.49 Hz.

b)

source moving away from the observer at rest requires the formula: f' = f / (1 + Vsource / Vsnd)

f' = 1550 / (1 + 32 / 343)

f' = 1417.73 Hz.