A galloping pony speeds past you at 5 m/s. The frequency of the sound produced by the hooves on the dirt is 221 Hz. Assume the speed of sound to be 342 m/s. What is the observed frequency of the hooves after the pony has passed your position?

1. 218 Hz

2. 226 Hz

3. 216 Hz

4. 224 Hz

Given:

speed of passing pony 5 m/s

frequency of the sound produced: 221 Hz

speed of sound 342 m/s

Let us use the Doppler Shift Formula:

Where the source is moving away from the observer at rest

f' = (v / v+vs) f

Where, vs = Velocity of the Source,

v = Velocity of sound or light in medium,

f = Real frequency,

f' = Apparent frequency.

f' = [342 m/s / (342 m/s+5m/s) ] * 221 Hz

f' = 0.9856 * 221Hz

f' = 217.8176 Hz or 218 Hz

The observed frequency of the hooves after the pony has passed your position is 218 Hz.

The answer is A) 218 Hz