1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
IgorC [24]
3 years ago
11

A police car is driving down the street with it's siren on. You are standing still on the sidewalk beside the street. If the fre

quency of the siren is 1500 Hz and the car is moving towards you at 15 m/s, what is the frequency you would hear from the siren? (v of sound in air = 343 m/s) (1 point)
1568.60 Hz
1321.43 Hz
2019.11 Hz
1676.92 Hz


If the same police car in question 1 has passed you and is now moving away from you at the same speed, what is the frequency you will hear from the siren? (1 point)
1198.67 Hz
1390.41 Hz
1437.15 Hz
1781.55 Hz
Physics
1 answer:
AleksandrR [38]3 years ago
3 0

Answer:

A) 1568.60 Hz

B) 1437.15 Hz

Explanation:

This change is frequency happens due to doppler effect

The Doppler effect is the change in frequency of a wave in relation to an observer who is moving relative to the wave source

f_(observed)=\frac{(c+-V_r)}{(C+-V_s)} *f_(emmited)\\

where

C = the propagation speed of waves in the medium;

Vr= is the speed of the receiver relative to the medium,(added to C, if the receiver is moving towards the source, subtracted if the receiver is moving away from the source;

Vs= the speed of the source relative to the medium, added to C, if the source is moving away from the receiver, subtracted if the source is moving towards the receiver.

A) Here the Source is moving towards the receiver(C-Vs)

and the receiver is standing still (Vr=0) therefore the observed frequency should get higher

f_(observed)=\frac{C}{C-V_s} *f_(emmited)\\=\frac{343}{343-15}*1500\\ =1568.60 Hz

B)Here the Source is moving away the receiver(C+Vs)

and the receiver is still not moving (Vr=0) therefore the observed frequency should be lesser

f_(observed)=\frac{C}{C+V_s} *f_(emmited)\\=\frac{343}{343+15}*1500\\ =1437.15 Hz

You might be interested in
ANSWER ALL QUESTIONS AND GET 100 PONTS ALONG WITH BRAINLIEST
dmitriy555 [2]

Answer:

  • To not exceed the 5,000 characters, see each answer with its explanation below.

Explanation:

<u><em>Question 1.</em></u>

<em>A feather and a rock dropped at the same time from the same height would land at the same time when dropped by an astronaut on the moon</em>.

The shape and mass of the <em>feather</em> that falls vertically down, through the air, cause the resistance of the air, that opposes the gravitational attraction of the Earth, to be considerably large, compared to the case of the <em>rock</em>.

This not negligible resistance of the air causes a drag on the <em>feather</em> that makes it fall more slowly than the <em>rock</em>.

Only on the moon, the almost absence of atmosphere (air) would cause the <em>feather</em> not to be dragged and, therefore, its acceleration will be the same as that of the rock, and both will fall with the same speed and land at the same time (there is a video in the internet that shows this experiment of the astronaut on the moon).

<em><u>Question 2.</u></em>

<em>When the soccer ball is kicked, the action and reaction forces do not cancel each other out because the forces act on two different objects.</em>

The third law of Newton, also known as the law of action and reaction, states that whenever an object experience a force (action force) from a second object, the first object will exert a force of equal size and opposite in direction (reaction force) over the second object.

Hence, the action and reaction forces act over distinct objects. The ball feels the action force (the kick) and the foot feels the reaction force from the ball; the forces do not cancel each other because they act on two different objects.

<u><em>Question 3 </em></u>

<em>An object is in projectile motion if it is thrown with a horizontal push.</em>

The <em>projectile motion</em> is the combination of two motions: vertical motion and horizonal motion.

The vertical motion is ruled by the acceleration of gravity and will depend on both the inital vertical velocity and the acceleration of gravity.

The horizontal motion is ruled by the horizontal velocity. According with the inertia law (first law of Newton), in the absence of a horizontal force, only if the object departs with a horizontal velocity it will move horizontally.

Hence, an object can only be in projectile motion if it is thrown with a horizontal push.

<u><em>Question 4 </em></u>

Acceleration of an object

  • increases as the force on the object increases.
  • decreases as the mass of the object increases.
  • is in the same direction as the force on the object.
  • All answers listed.    ← correct answer

According to second law of Newton

          \vec{F}=m\times \vec{a}

This is force equals mass time acceleration.

The force is a vector and the acceleration is a vector, then since mass is a positive scalar magnitude, both force and acceleration have the same direction.

Also, it is clear from the definition of force that it is proportional to both, the mass and the acceleration, then if either mass or acceleration increases (while the other remains equal) the force will increase, and if either mass or acceleration decreases (while the other remains constant) the force will decrease.

Hence, all the options are correct.

<u><em>Question 5</em></u>

<em>The bowling ball will have more momentum because it has more mass.</em>

Momentum, P, is the product of the mass (m) and the velocity (v).

           \vec{P}=m\times \vec{v}

It is clear that the mass of the bowling ball is greater than the mass of the golf ball.

Hence, since they are moving at the same velocity, the product of the mass of the bowling ball times the velocity is greater than the product of the golf mass times the same velocity.

<u><em>Question 6</em></u>

<em>An  </em><em><u>   orbit         </u></em><em> is formed when an object is falling around another object, rather than into it.</em>

An example of an object falling around another object is a rock falling in the Earth. The gravitaional pull of the Earth causes that the rock accelerates and falls vertically downward.

An example of an object falling around another object is a satellite around the Earth.

The Earth is continually pulling the satellite with vertical force and the inertia (initial velocity) of the satellite is causing it to move horizontally.

The combination of the gravitational force and the inertia cause the satellite to follow a projectile motion. When the satellite is to the correct distance it will not reach into the Earth but will continually move around the Earth following a circular path named orbit.

<u>Question 7</u>

<em>When the force of gravity is matched by the force of air resistance, an object can reach  </em><em><u>    terminal velocity      </u></em><em>(two word answer).</em>

When the force of gravity matches the force of air resistance, the net force on the falling object is zero.

Hence, as per the second Law of Newton, force equals the product of the mass and the acceleration, the acceleration is also zero.

Zero acceleration means constant velocity.

That constant velocity is a limit or maximum for the velocity that an object can reach when falling and is called terminal velocity.

3 0
2 years ago
Background information about reflection and refraction of light
KIM [24]

Answer:

reflection :

  • angle of reflection and angle of incidence is equal
  • Incident ray and reflect d ray plus normal lies on the same plan on a same point
  • light reflect uniformly if it is incident on a plan surface

refraction :

  • light will refrect if light goes from rare medium to a dense medium or vice versa
  • after the light is refracted, it retunes to its original direction
  • angle of incidence is not equal to the angle of refraction
4 0
3 years ago
The Heaviside function H is defined by H(t)={0 if t&lt;0, 1 if t≥0 It is used in the study of electric circuits to represent the
Studentka2010 [4]

Answer:

V(t)= 240V* H(t-5)

Explanation:

The heaviside function is defined as:

H(t) =1 \quad t\geq 0\\H(t) =0 \quad t

so we see that the Heaviside function "switches on" whent=0, and remains switched on when t>0

If we want our heaviside function to switch on when t=5, we need the argument to the heaviside function to be 0 when t=5

Thus we define a function f:

f(t) = H(t-5)

The -5 term inside the heaviside function makes sure to displace the function 5 units to the right.

Now we just need to add a scale up factor of 240 V, because thats the voltage applied after the heaviside function switches on. (H(t-5) =1 when t\geq 5, so it becomes just a 1, which we can safely ignore.)

Therefore our final result is:

V(t)= 240V* H(t-5)

I have made a sketch for you, and added it as attachment.  

5 0
3 years ago
Determine the CM of a rod assuming its linear mass density λ (its mass per unit length) varies linearly from λ = λ0 at the left
Dahasolnce [82]

Answer:

x_c= \dfrac{5}{9}L

I=\dfrac {7}{12}\lambda_ 0 L^3

Explanation:

Here mass density of rod is varying so we have to use the concept of integration to find mass and location of center of mass.

At any  distance x from point A mass density

\lambda =\lambda_0+ \dfrac{2\lambda _o-\lambda _o}{L}x

\lambda =\lambda_0+ \dfrac{\lambda _o}{L}x

Lets take element mass at distance x

dm =λ dx

mass moment of inertia

dI=\lambda x^2dx

So total moment of inertia

I=\int_{0}^{L}\lambda x^2dx

By putting the values

I=\int_{0}^{L}\lambda_ ox+ \dfrac{\lambda _o}{L}x^3 dx

By integrating above we can find that

I=\dfrac {7}{12}\lambda_ 0 L^3

Now to find location of center mass

x_c = \dfrac{\int xdm}{dm}

x_c = \dfrac{\int_{0}^{L} \lambda_ 0(1+\dfrac{x}{L})xdx}{\int_{0}^{L} \lambda_0(1+\dfrac{x}{L})}

Now by integrating the above

x_c=\dfrac{\dfrac{L^2}{2}+\dfrac{L^3}{3L}}{L+\dfrac{L^2}{2L}}

x_c= \dfrac{5}{9}L

So mass moment of inertia I=\dfrac {7}{12}\lambda_ 0 L^3 and location of center of mass  x_c= \dfrac{5}{9}L

8 0
3 years ago
Help me please, need more assistance
Dmitrij [34]

Explanation:

12) q = mCΔT

125,600 J = (500 g) (4.184 J/g/K) (T − 22°C)

T = 82.0°C

13) Solving for ΔT:

ΔT = q / (mC)

a) ΔT = 1 kJ / (0.4 kg × 0.45 kJ/kg/K) = 5.56°C

b) ΔT = 2 kJ / (0.4 kg × 0.45 kJ/kg/K) = 11.1°C

c) ΔT = 2 kJ / (0.8 kg × 0.45 kJ/kg/K) = 5.56°C

d) ΔT = 1 kJ / (0.4 kg × 0.90 kJ/kg/K) = 2.78°C

e) ΔT = 2 kJ / (0.4 kg × 0.90 kJ/kg/K) = 5.56°C

f) ΔT = 2 kJ / (0.8 kg × 0.90 kJ/kg/K) = 2.78°C

14) q = mCΔT

q = (2000 mL × 1 g/mL) (4.184 J/g/K) (80°C − 20°C)

q = 502,000 J

20) q = mCΔT

q = (2000 g) (4.184 J/g/K) (100°C − 15°C) + (400 g) (0.9 J/g/K) (100°C − 15°C)

q = 742,000 J

24) q = mCΔT

q = (0.10 g) (0.14 J/g/K) (8.5°C − 15°C)

q = -0.091 J

6 0
3 years ago
Other questions:
  • A proton is moving at 425 m/s. (a) How much work must be done on it to stop it? (A proton has a mass of 1.67×10−27 kg.) (b) Assu
    6·1 answer
  • Please List 3 categories of properties used to classify solids.
    12·1 answer
  • A box is sitting on the ground and weighs 100 kg and the coefficient of friction is 0.23. Is it easier to push by applying the f
    7·1 answer
  • Explain how you can change your workout routine using each of the SPORT and FITT principles.
    15·1 answer
  • A piece of charcoal used for cooking is found at the remains of an ancient campsite. A 1.09 kg sample of carbon from the wood ha
    6·1 answer
  • How many planets are in our solar system
    13·2 answers
  • What material most likely would form a aquiclude?
    14·1 answer
  • Galileo was the first scientist to do which of the following? A. estimate the speed of light B. propose the heliocentric theory
    11·2 answers
  • The speed of a light wave in a certain transparent material is 0.589 times its speed in vacuum, which is 3.00 x108 m/s. When yel
    9·1 answer
  • Pls help me Will mark you as brain plssss help me for these 2 questions just say top or bottom for which answers you pick
    13·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!