A whistle giving out 450hz approaches stationary observe at a speed of 33m/s. What is the frequency heard by the observer ? ( velocity of sound in air=330m/s)

Answer 1

The observed frequency can be calculated using the Doppler effect formula:

f' = f * (v_sound +/- v_observer) / (v_sound +/- v_source)

where:
f = original frequency of the whistle (given as 450 Hz)
v_sound = velocity of sound in air (given as 330 m/s)
v_observer = velocity of the observer (given as 33 m/s in the opposite direction)
v_source = velocity of the source (assumed to be stationary)

Plugging in the values:

f' = 450 * (330 - 33) / (330 + 0)
f' = 450 * 297 / 330
f' = 405 Hz (rounded to the nearest Hz)

Therefore, the frequency heard by the observer is 405 Hz.