1)As a sound source moves away from a stationary observer, the number of waves will.

decrease

2)How fast should a car move toward you for the car's horn to sound 2.88% higher in frequency than when the car is stationary? The speed of sound is 343 m/s.

fs(v-vd/v-vs)
343(1/1-987/343)

A)4.5 m/s
B)7.3 m/s
C)9.6 m/s
D)11.8 m/s

I'm doing something wrong I got D (well I guessed D)

3)A car moving at 16.0 m/s, passes an observer while its horn is pressed. Find the difference between the frequencies of sound heard when the car approaches and when it recedes from the stationary observer. The velocity of sound is 343 m/s and the frequency of the sound of the car's horn is 583 Hz.

4)A boy is blowing a whistle of frequency 536 Hz and walking toward a wall with a speed of 1.64 m/s. What frequency of the reflected sound will the boy hear if the speed of sound is 343 m/s?

1) As a sound source moves away from a stationary observer, the number of waves will decrease. This is because as the source moves away, each successive wave takes longer to reach the observer. Therefore, the frequency of the waves decreases, resulting in fewer waves reaching the observer per unit of time.

2) To determine the speed at which the car should move toward the stationary observer for the car's horn to sound 2.88% higher in frequency, we can use the formula for the Doppler effect:

fs = fo * (v + vd) / (v + vs)

Where:
fs = frequency heard by the stationary observer
fo = original frequency of the sound source (car's horn)
v = speed of sound in air (343 m/s)
vd = velocity of the observer (0 m/s, since the observer is stationary)
vs = velocity of the sound source towards the observer (which we need to find)

By substituting the given values into the formula and solving for vs, we can find the required velocity of the car towards the observer:

fs = 1.0288 * fo
343 = 1.0288 * fo
fo = 343 / 1.0288 ≈ 333.91 Hz

Now we can plug this value of fo back into the formula:

333.91 = (343 + 0) / (343 + vs)
vs = 343 - (343 * 333.91) / 333.91 ≈ 11.8 m/s

Therefore, the correct answer is D) 11.8 m/s.

Note: In your calculation, it seems you made a mistake by subtracting the fractions instead of dividing them and dividing 343 by 987 instead of multiplying them. Make sure to follow the proper mathematical operations to obtain the correct result.

3) To find the difference between the frequencies of sound heard when the car approaches and when it recedes from the stationary observer, we can use the formula for the Doppler effect:

Δf = fs - fo

Where:
Δf = difference in frequency
fs = frequency heard by the stationary observer
fo = original frequency of the sound source (car's horn)
v = speed of sound in air (343 m/s)
vd = velocity of the observer (0 m/s, since the observer is stationary)
vs = velocity of the sound source (16.0 m/s, as given)

By substituting the given values into the formula, we can calculate the difference in frequency:

fs = fo * (v + vd) / (v + vs)
fs = 583 * (343 + 0) / (343 + 16)
fs ≈ 583 Hz

Δf = fs - fo
Δf = 583 - 583
Δf = 0 Hz

Therefore, the difference between the frequencies of sound heard when the car approaches and when it recedes from the stationary observer is 0 Hz.

4) To calculate the frequency of the reflected sound that the boy will hear, we can use the formula for the Doppler effect:

fs = fo * (v - vd) / (v - vs)

Where:
fs = frequency heard by the observer
fo = original frequency of the sound source (whistle)
v = speed of sound in air (343 m/s)
vd = velocity of the observer (1.64 m/s)
vs = velocity of the sound source (0 m/s, since the wall is stationary)

By substituting the given values into the formula, we can calculate the frequency heard by the boy:

fs = 536 * (343 - 1.64) / (343 - 0)
fs ≈ 529.68 Hz

Therefore, the boy will hear a frequency of approximately 529.68 Hz for the reflected sound.