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:
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Nope. It means that the density of the object is less than the density of the water it's in, making it float. Conversely, if the density of an object is greater than the density of the water it's in, then the object will sink. :)
Answer:
The correct answer is a. Both are the same
Explanation:
For this calculation we must use the gravitational attraction equation
F = G m M / r²
Where M will use the mass of the Earth, m the mass of the girl and r is the distance of the girl to the center of the earth that we consider spherical
To better visualize things, let's repair the equation a little
F = m (G M / r²)
The amount in parentheses called acceleration of gravity, entered the force called peos
g = G M / r²
F = W
W = m g
When analyzing this equation we see that the variation in the weight of the girl depends on the distance, which is the radius of the earth plus the height where the girl is
r = Re + h
Re = 6.37 10⁶ m
r² = (Re + h)²
r² = Re² (1 + h / Re)²
Let's replace
W = m (GM / Re²) (1+ h / Re)⁻²
W = m g (1+ h / Re)⁻²
This is the exact expression for weight change with height, but let's look at its values for some reasonable heights h = 6300 m (very high mountain)
h / Re = 10
⁻³
(1+ h / Re)⁻² = 0.999⁻²
Therefore, the negligible weight reduction, therefore, for practical purposes the weight does not change with the height of the mountain on Earth
The correct answer is a
Number 3.
When you have two parallel wire and the charges are moving, they create a magnetic field around the wire (right-hand rule, thumb points in the direction of current).
If you want the math, here ya go:
F: magnetic force on the wire, L: length of the wire I: current in one wire I': current in other wire r: distance of the wire.
As we can see, two wires that has current through it will generate a force on each other.
C. the order from closest to the sun to furthest is Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune so C. would be the opposite heading towards the sun. A good mnemonic to use is MVEMJSUN: My Very Educated Mother Just Served Us Nectarines
