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

A)increase
B)decrease
C)remain the same
D)need to know the speed of the source

(answer:decrease.) As the detector recedes from the source, the relative velocity is smaller, resulting in a decrease in the wave crests reaching the detector each second. (thats from the book)

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.

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?

I really don't have a clue on the last 3, I've been trying for 2 days but I don't understand, can I get a formula or SOMETHING ANYTHING

OK, here are Doppler effect recipes for wave speed v, frequency Fs:

Moving listener:
Listener L moving toward Stationary source S with speed Vl (Vl negative if moving away)
Fl = (v+Vl)/lambda = (v+Vl)/(v/Fs)
or
Fl = [ (v+Vl)/v ] Fs

Moving source
If the source is also moving:
Vs is speed of source, positive if moving AWAY from listener.
Fl = { (v+Vl)/(v+Vs) ] Fs

in the final problem, first do the source whistle approaching the reflector listener (Vl = 0, Vs = -16m/s). Get the frequency felt by the wall, which is what it will send back. then do the listener moving toward a stationary source.

Sure! I can help you with these questions. All of these questions involve the Doppler effect, which is the change in frequency or wavelength of a wave as observed by someone moving relative to the source of the wave.

Let's start with question 2:

To solve this problem, we can use the equation for the Doppler effect when the source is moving towards the observer:

f' = (v + v₀) / v * f₀,

where f' is the observed frequency, v is the speed of sound, v₀ is the speed of the source, and f₀ is the frequency emitted by the source.

In this case, we want f' to be 2.88% higher than f₀. So, we can write:

f' = (1 + 0.0288) * f₀.

Then, we can substitute this into the Doppler equation and solve for v₀:

(1 + 0.0288) * f₀ = (v + v₀) / v * f₀.

Simplifying the equation, we get:

(1 + 0.0288) * v = v + v₀.

Now, we can solve for v₀:

v₀ = (1 + 0.0288) * v - v.

Now, just plug in the values you were given: v = 343 m/s and f₀ is the frequency emitted by the car's horn.

Moving on to question 3:

This question asks for the difference between the frequencies of sound heard when the car approaches and when it recedes from the observer. Let's call these frequencies f'₁ and f'₂, respectively.

The general formula for the Doppler effect when the source is moving is:

f' = (v + v₀) / (v ± vo) * f₀,

where the plus sign is used for approaching, and the minus sign is used for receding.

In this case, we want to find the difference between f'₁ and f'₂, so we can subtract the two equations:

f'₁ - f'₂ = [(v + v₀) / (v + vo) - (v + v₀) / (v - vo)] * f₀.

Now, substitute the given values: v = 343 m/s, v₀ = 16.0 m/s, and f₀ = 583 Hz.

Finally, rearrange the equation to solve for f'₁ - f'₂.

Now, for question 4:

This question also relates to the Doppler effect when the source is moving. The formula is the same as in question 3.

Given that the boy is walking toward a wall, the wall acts as a stationary observer. So, we need to calculate the frequency of the reflected sound that the boy will hear.

Again, use the Doppler equation with the minus sign to indicate the source is receding:

f' = (v + v₀) / (v - vo) * f₀.

Substitute the given values: v = 343 m/s, v₀ = 1.64 m/s, and f₀ = 536 Hz.

This should help you solve the last three questions. Let me know if you need any further assistance!