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3 years ago

What is the wavelength (in air) of a 13.0 khz vlf radio wave?

1 answer:

5 0

Since,
Speed = Frequency * WaveLength

=> WaveLength = Speed / Frequency --- (A)

Frequency = 13.0 kHz.
As the radio waves are electromagnetic waves, their speed is equals to the speed of light. Therefore,
Speed = C = $3 * 10^{8} m/ s^{2}$

Plug in the values in equation(A):

A => WaveLength = $\frac{3 * 10^{8}}{13*10^{3}}$

Ans: Wavelength = 23.077 kilometers.
-i

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What is the reaction force of the table with a weight of 558N

Delicious77 [7]

Answer: reaction force = -558N

Explanation:

w = f = 558N

since action force and reaction force are equal in magnitude and opposite in direction,

reaction force = -(f)

reaction force = -558N

if that helps.

8 0

3 years ago

Which statement best describes insulators? Free electrons can move to other atoms Electrons within their atoms are strongly held

balandron [24]

Answer:

The statement that best describes insulators is "Electrons within their atoms are strongly held by the nuclei"

Explanation:

Atoms are constituted by a nucleus with positive charge (protons and neutrons), around which negative charges (electrons) revolve.

Substances that have a huge amount of "free electrons" that can move through the material are called conductors. This is due to the low resistance to the movement of the load or electric current.

Materials that do not conduct electricity are called insulators. In this case the electrons are strongly bound to the nucleus and cannot move freely. In this way a great resistance to the flow of electric current is offered.

Finally, semiconductors are the materials that can have electrical properties of conductors or insulators.

So the statement that best describes insulators is "Electrons within their atoms are strongly held by the nuclei"

7 0

3 years ago

A student pushes against a wall with a force of 30N. The wall does not move. What amount of force does the wall exert on the stu

True [87]

Answer:

Explanation:

they both have to be the same for both to not move

8 0

2 years ago

Read 2 more answers

You are traveling in a car toward a hill at a speed of 36.4 mph. The car's horn emits sound waves of frequency 231 Hz, which mov

Marina CMI [18]

Answer:

a. The frequency with which the waves strike the hill is 242.61 Hz

b. The frequency of the reflected sound wave is 254.23 Hz

c. The beat frequency produced by the direct and reflected sound is

11.62 Hz

Explanation:

Part A

The car is the source of our sound, and the frequency of the sound wave it emits is given as 231 Hz. The speed of sound given can be used to determine the other frequencies, as expressed below;

$f_{1} = f[\frac{v_{s} }{v_{s} -v} ]$ ..............................1

where $f_{1}$ is the frequency of the wave as it strikes the hill;

f is the frequency of the produced by the horn of the car = 231 Hz;

$v_{s}$ is the speed of sound = 340 m/s;

v is the speed of the car = 36.4 mph

Converting the speed of the car from mph to m/s we have ;

hint (1 mile = 1609 m, 1 hr = 3600 secs)

v = $36.4 mph *\frac{1609 m}{1 mile} *\frac{1 hr}{3600 secs}$

v = 16.27 m/s

Substituting into equation 1 we have

$f_{1}$ = $231 Hz (\frac{340 m/s}{340 m/s - 16.27 m/s})$

$f_{1}$ = 242.61 Hz.

Therefore, the frequency which the wave strikes the hill is 242.61 Hz.

Part B

At this point, the hill is the stationary point while the driver is the observer moving towards the hill that is stationary. The frequency of the sound waves reflecting the driver can be obtained using equation 2;

$f_{2} = f_{1} [\frac{v_{s}+v }{v_{s} } ]$

where $f_{2}$ is the frequency of the reflected sound;

$f_{1}$ is the frequency which the wave strikes the hill = 242.61 Hz;

$v_{s}$ is the speed of sound = 340 m/s;

v is the speed of the car = 16.27 m/s.

Substituting our values into equation 1 we have;

$f_{2} = 242.61 Hz [\frac{340 m/s+16.27 m/s }{340 m/s } ]$

$f_{2}$ = 254.23 Hz.

Therefore, the frequency of the reflected sound is 254.23 Hz.

Part C

The beat frequency is the change in frequency between the frequency of the direct sound and the reflected sound. This can be obtained as follows;

Δf = $f_{2}$ - $f_{1}$

The parameters as specified in Part A and B;

Δf = 254.23 Hz - 242.61 Hz

Δf = 11.62 Hz

Therefore the beat frequency produced by the direct and reflected sound is 11.62 Hz

3 0

3 years ago

Question I. SUHU ULT

Lilit [14]

Answer:

Feathers are great thermal insulators.

Explanation:

Feathers are great thermal insulators. The loose structure of down feathers traps air.

As a result, energy cannot be transmitted easily through down feathers. This means birds are insulated from cold air outside, plus their body heat doesn't escape easily either.

Human beings discovered that down feathers are good for insulation long ago. For example, documents from the 1600s show that Russian merchants sold “bird down" to the Dutch hundreds of years ago.

Today, down is used in all sorts of products, including coats, bedding, and sleeping bags, to help better insulate the user from cold weather. Down can be collected from many different types of birds, but most of today's supply comes from domestic geese.

If you have a down coat or comforter, is it all down? In the United States, laws require that products labeled “100 percent down" contain only down feathers.

If your product is labeled “down," it can contain a mixture of both down feathers and synthetic fibers. Not all down feathers are created equal, though.

Down insulation is rated on a measure called “fill power." The higher the fill power, the more the down insulates.

The highest fill-power rating — 1200 — goes to eiderdown, which comes from the Common Eider duck. Eiderdown tends to be expensive.

3 0

3 years ago