How states of matter can change forms

A student hears a police siren. What would change the frequency that the student hears? check all that apply

andriy [413]

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:

$f'=f\frac{v+-vR}{v-+vE}$

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

We will use the - sign:

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

#SPJ12

7 0

2 years ago

When you need to pass a motorcycle, _____________.A. move into the left lane to pass the motorcycle B. pass to the left using th

erma4kov [3.2K]

Answer:

A) move into the left lane to pass the motorcycle

Explanation:

According to law, when it is needed to pass other vehicles, it requires you to only pass other vehicles on the left (using the left lane).

When passing a motorcyclist, remember to give him/her the same full lane width as other vehicles. Never drive in the same lane with a motorcyclist, even if the lane is wide enough to fit your vehicle and the motorcyclist.

5 0

4 years ago

A cart moves with negligible friction or air resistance along a roller coaster track. The cart starts from rest at the top of a

lina2011 [118]

Answer:

hinit = 17.5 m

Explanation:

Assuming no friction present, the mechanical energy must be conserved, which means that at any point of the trajectory, the sum of the gravitational potential energy and the kinetic energy must keep the same.
At the top of the hill, since it starts from rest, all the energy must be potential, and we can express it as follows:

$E_{o} = U_{o} = m*g*h_{init} (1)$

When the car arrives to the top of the second hill, as we know that it is lower than the first one, the energy of the car, must be part gravitational potential energy, and part kinetic energy.
We can express this final energy as follows:

$E_{f} = U_{f} + K_{f} = m*g* h_{2} + \frac{1}{2} *m*v_{f} ^{2} (2)$

In order to find hinit, we need to make (1) equal to (2), and solve for it.
In (2) we have the value of h₂ (10 m), but we still need the value of the speed at the top of the second hill, vf.
Now, when the car is at the top of the hill, there are two forces acting on it, in opposite directions: the normal force (upward) and the weight (downward).
We know also that there is a force that keeps the car along the circular track, which is the centripetal force.
This force is just the net downward force acting on the car (it's vertical at the top), and is just the difference between the weight and the normal force.
If the cart just barely loses contact with the track at the top of the second hill, this means that at that point the normal force becomes zero.
So, the centripetal force must be equal to the weight.
The centripetal force can be expressed as follows:

$F_{c} = m*\frac{v_{f} ^{2}}{R} (3)$

We have just said that (3) must be equal to the weight:

$F_{c} = m*\frac{v_{f} ^{2}}{R} = m*g (4)$

Simplifying, and rearranging, we can solve for vf², as follows:

$v_{f}^{2} = R*g (5)$

Replacing (5) in (2), simplifying and rearranging in (1) and (2) we finally have:

$h_{init} = h_{2} + \frac{1}{2} R = 10m + 7.5 m = 17.5 m (6)$

7 0

3 years ago

Why will a change in velocity have a greater affect on KE than a change in mass?

Sever21 [200]

Answer: the answer is corect of what everone else said

Explanation:

5 0

3 years ago

Read 2 more answers

What is the sum of all forces acting on an object and direction

babunello [35]

The sum of all forces on an object is the net force or resultant force. If all the forces cancel out , resultant force is zero , otherwise unbalanced force will cause acceleration of object .

Force is the vector, has both direction and magnitude.

3 0

3 years ago