Considering the Doppler efect, the frequency heard by the student would change if:
- if the student walked toward the police car.
- if the student walked away from the police car.
- if the police car moved toward the student.
- if the police car moved away from the student.
<h3>Doppler effect</h3>
The Doppler effect is defined as the change in the apparent frequency of a wave produced by the relative motion of the source with respect to its observer. In other words, this effect is the change in the perceived frequency of any wave motion when the sender and receiver, or observer, move relative to each other.
The following expression is considered the general case of the Doppler effect:

Where:
- f', f: Frequency perceived by the receiver and frequency emitted by the transmitter, respectively. Its unit of measurement in the International System (S.I.) is the hertz (Hz), which is the inverse unit of the second (1 Hz = 1 s⁻¹)
- v: Wave propagation speed in the medium. It is constant and depends on the characteristics of the medium. In this case, the speed of sound in air is considered to be 343 m/s.
- vR, vE: Receiver and transmitter speed respectively. Its unit of measure in the S.I. is the m/s
- ±, ∓:
- We will use the + sign:
- In the numerator if the receiver approaches the sender
- In the denominator if the sender moves away from the receiver
- In the numerator if the receiver moves away from the sender
- In the denominator if the sender approaches the receiver
In summary, the Doppler Effect is an alteration of the observed frequency of a sound due to the movement of the source or the observer, that is, they are changes in the frequency and wavelength of a wave due to the relative movement between the wave source and the observer.
<h3>Changes on the frequency </h3>
In this case, considering the Doppler effect, the frequency heard by the student would change if:
- if the student walked toward the police car.
- if the student walked away from the police car.
- if the police car moved toward the student.
- if the police car moved away from the student.
Learn more about Doppler effect:
brainly.com/question/15307081
brainly.com/question/4052291
brainly.com/question/15097772
brainly.com/question/3841958
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Last month, we featured IRB best practices (“IRBs: Navigating the Maze” November 2007 Observer), and got the ball rolling with strategies and tips that psychological scientists have found to work. Here, we continue the dissemination effort with the second of three articles by researchers who share their experiences with getting their research through IRB hoops. Jerry Burger from Santa Clara University managed to do the seemingly impossible — he conducted a partial replication of the infamous Milgram experiment. Read on for valuable advice, and look for similar coverage in upcoming Observers. These are the first words I said to Muriel Pearson, producer for ABC News’ Primetime, when she approached me with the idea of replicating Stanley Milgram’s famous obedience studies. Milgram’s work was conducted in the early 1960s before the current system of professional guidelines and IRBs was in place. It is often held up as the prototypic example of why we need policies to protect the welfare of research participants. Milgram’s participants were placed in an emotionally excruciating situation in which an experimenter instructed them to continue administering electric shocks to another individual despite hearing that person’s agonizing screams of protest. The studies ignited a debate about the ethical treatment of participants. And the research became, as I often told my students, the study that can never be replicated. Hope this helps!
Answer:
D. The liquid has absorbed as much heat as it can until it starts to vaporize.
Explanation:
Below is an attachment containing the solution.