If a car whose horn emits a frequency of 500 Hz is driving toward you at 30 m/s, which frequency might be the one that you hear?
550hz
550 hz
Well, if a car with a horn emitting a frequency of 500 Hz is driving toward you at 30 m/s, the frequency you might hear could be something like "Aaaaaahhhhhhhhhhhh!!!" Sorry, I couldn't resist adding a touch of clownish humor to your question. In all seriousness, you would actually hear a higher frequency than 500 Hz due to the Doppler effect. As the car approaches you, the sound waves get compressed, resulting in a higher perceived frequency. So, buckle up and get ready to hear a slightly higher-pitched horn!
To determine the frequency that you might hear from the moving car's horn, we need to apply the concept of the Doppler effect. The Doppler effect describes the change in frequency or wavelength of a wave as it approaches or moves away from an observer.
In this case, as the car is approaching you, the sound waves emitted by the car's horn will be compressed, resulting in a higher frequency. Conversely, if the car is moving away from you, the sound waves will be stretched, resulting in a lower frequency.
To calculate the frequency you might hear, we can use the following formula:
f' = (v + vd)/(v + vs) * f
Where:
f' = observed frequency
f = emitted frequency (500 Hz)
v = speed of sound in air (approximately 343 m/s at 20°C)
vd = velocity of the car relative to the observer (-30 m/s since the car is driving towards you)
vs = velocity of the sound relative to the observer (0 since you are stationary)
Plugging in the values into the formula:
f' = (343 + (-30)) / (343 + 0) * 500 Hz
Simplifying this equation gives us:
f' = (313 / 343) * 500 Hz
Calculating this expression:
f' ≈ 457.5 Hz
Therefore, the frequency that you might hear from the car's horn as it drives towards you at 30 m/s is approximately 457.5 Hz.
F = (Vs+Vo)/(Vs-Vh) * Fh.
F = (343+0)/(343-30) * 500 =
Vs = velocity of sound.
Vo = velocity of the observer.
Vh = velocity of the horn.