Please help

how long have people used coal as a source of fuel
A. 200 years
B. 1000 years
C. 3000 years
D. 5000 years

Answers

Answer 1

Answer:

c. 3,000

Explanation:

I am guessing 3000 years


Related Questions

How would the removal of the rabbit population affect the other populations in

the ecosystem?

A.

B.

The field mouse population will decrease.

The snake population will increase.

The lizard population will increase.

The tree population will decrease.

C.

D.

Answers

C the lizard population will increase

How much work do you do on a 25- kg backpack when you walk a horizontal distance of 100m ?

Answers

Answer:

2,500

Explanation:

Distinguish between infrasonic and ultrasonic sound waves.

Answers

How we could distinguish them is that the infrasonic sounds are the lower limit of human hearing while ultrasonic sound is above human hearing. The sound of frequency more than 20,000Hz are called ultrasonics while the frequency less than 20Hz are called infrasonics.

Explanation:

I hope it helps! Have a great day!

Anygays-

A scientist adds different amounts of salt to 5 bottles of water. She then measures how long it takes for the water to boil. What is the responding variable in this experiment? 0 A. The kind of bottles used O B. The brand of salt used O C. The amount of salt added to the water O D. The time it takes for the water to boil

Answers

Answer:

d.the time it takes for the water to boil

Explanation:

it is because salt was added to the water.so the responding variable is the time taken to boil the water

A force of 20 N is applied tangentially to a wheel of mass 10 kg and diameter 5 m. Calculate the torque applied and angular velocity at the end of 10 second?​

Answers

Answer:

N = 20

10 + 10 + -5 = 20

N + -5 = 10 -5 + 20

Therefore , the answer is N=20

Explanation:

#BrainliestBunch

For brainliest and 100 points
Ben is pushing a small trolley 10 N to the north and but Gary is pushing the trolley 5 N to the south. What is the total applied force on the trolley?

5N
2N
20N
40N

Answers

Answer:

The total applied force on the trolley is 5 N toward the North.

Explanation:

yes

Two thermometers are calibrated, one in degrees Celsius and the other in degrees Fahrenheit. At what temperature are their readings numerically the same

Answers

Answer:

To change degrees Celsius in degrees Fahrenheit, the formula is:

F = 1.8C +32F=1.8C+3

Explanation:

C = 1.8C +32C=1.8C+32

C = -40C=−40

T=-40+273.15=233.15\ KT=−40+273.15=233.15 K

Levi observed properties of three different waves and recorded observations about each one in his chart. which statement is best supported by the table? wave w and y are light waves. wave x is a sound wave. wave w is a light wave. waves x and y are sound waves. waves y is a sound wave. waves x and w are light waves. wave w is a sound wave. waves x and y are light waves.

Answers

For the three different waves observed and recorded, Waves X and Y are light waves. This is further explained below.

What is a wave?

Generally, A wave is simply defined as a disturbance that propagates through a medium from one point to another.

In conclusion,  Wave Z is impossible to classify, Waves X and Y are light waves, and Wave W is a sound wave.

Read more about Wave

https://brainly.com/question/23271222

Answer:

D

Explanation:

How do you boost the amount of electricity a fuel cell system produces?.

Answers

For this one it should be A single fuel cell generates approximately one volt of electricity. Individual fuel cells are combined to form a fuel cell stack to enhance the amount of electricity produced.

The amount of electricity a fuel cell system produces is boost by combined to form a fuel cell that is battery.

What is battery?

A battery is a device that uses an electrochemical oxidation-reduction (redox) cycle to turn the chemical energy included in its active components directly into electric energy. An electric circuit is used in this kind of reaction to transmit electrons from one substance to another.

The actual elector-chemical unit used to produce or store electric

For this one it should be A single fuel cell generates approximately one volt of electricity. Individual fuel cells are combined to form a fuel cell stack to enhance the amount of electricity produced.

The amount of electricity a fuel cell system produces is boost by combined to form a fuel cell that is battery.

To learn more about battery refer to the link:

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The worker in the picture is
a.) letting the pulley do all the work
b.) not doing work because he is using a pulley
c.) doing work because he is moving the bale of cotton
d.) transforming mechanical energy to potential energy

Answers

Answer:

the worker is doing work because he is moving the bale of cotton

What is the momentum of an object that has a mass of 0.03 grams and a velocity of 1200 m/s2

Answers

answer is 36

because the formulae of momentum is

mass×velocity

Consider the following statements.

A. Heat flows from an object with higher
thermal energy to one with lower thermal energy;

B. Heat flows from an object at higher tem-
perature to an object at lower temperature;

C. Heat flows from an object in liquid state
to an object in solid state.

Which statements are true?

Answers

Answer:The heat flows from an object at a higher temperature to the object at a lower temperature. Thus the option A is correct.

Explanation:What is heat flow?


The flow of heat is the transfer of heat that concerns its generation, use and conversion, and exchange.The heat flow follows the laws of the thermodynamics. Heat will flow from the body that is at a higher temperature and will move towards a body of a lower temperature. Thereby maintaining an equilibrium state. As energy is needed to warm or heat up the cold body there is an exchange of energy that takes place.

For pea plants, T represents a dominant allele for tall pea plants and t is the recessive allele for short pea plants. If two plants with the Tt genotype are crossed, what is the probability that offspring will exhibit the dominant trait?

Answers

Answer:

75%(TT,Tt,tt) Hope that helps

Do people actually see me inverted?☹​

Answers

Answer:

of course is clear

Explanation:

very clear

(b) Fig. 7. 2 shows a metal sphere on an insulating support.

C

Fig. 7. 2

A student has available two rods, one charged positively and one charged negatively. Using

one of these rods, she gives the sphere a uniform negative charge by induction

State which rod she chooses, and describe the procedure she follows.

Answers

The rod she chooses, to give the sphere a uniform negative charge by induction is the positively charged rod.

Charging by induction

Charging an object by induction is a process of inducing a charge on the object by bringing another charged object close to it.

Charge on the sphere

When a positively charged rod is brought near a neutral sphere (equal negative and positive charge),  the positive charge of the rod will repel the positive charge of the sphere, leaving the sphere with excess negative charge.

Thus, the rod she chooses, to give the sphere a uniform negative charge by induction is the positively charged rod.

Learn more about charging by induction here: https://brainly.com/question/8418256

Since many wavelengths of light are measured in nanometers, it's useful to know that planck's constant (h) multiplied with the speed of
light (c) is equal to 1240 eVnm.
This is useful, as E = hf, or otherwise written as E= .
With this information in mind, solve the following:
A photon has 1.6 eV of energy. What is the wavelength of this photon?
O a
410 nm
Ob
775 nm
Ос
1984 nm
Od
306 nm

Answers

Answer:

E = h f      and since f = c / λ     we have E = h c / λ

Thus  λ = h c / E

Also, 1 ev = 1.6E-19 C

λ = 6.63E-34 * 3.0E8 / (1.6 * 1.6E-19)

λ = 6.63 * 3.0 / (1.6 * 1.6) * E-7

λ = 7.77E-7 = 777 nanometers

(B) is correct

Please help me with the blanks

Answers

Answer:

wavelength and frequency

Explanation:

wavelength is the distance between waves while frequency is the number of times in which the wave occurs.

Infrared radiation is part of a 'family' of waves that also includes visible light and radio waves. What name is given to this 'family'? Give the full name, not the abbreviation.

Answers

Electromagnetic spectrum

Infrared radiation is a part of electromagnetic waves,which also include the visible light and radio waves.

What are electromagnetic waves?

The electromagnetic radiation consists of waves made up of electromagnetic field which are capable of propogating through space and carry the radiant electromagnetic energy.

The radiation are composed of electromagnetic waves which are synchronized oscillations of electric and magnetic fields . They are created due to change which is periodic in electric as well as magnetic fields.

In vacuum ,all the electromagnetic waves travel at the same speed that is with the speed of air.The position of an electromagnetic wave in an electromagnetic spectrum is characterized by it's frequency or wavelength.They are emitted by electrically charged particles which undergo acceleration and subsequently interact with other charged particles.

Learn more about electromagnetic waves,here:

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Please help answer the following questions ASAP

Answers

Answer:

renewable are fuels that can be reused while non renewable are fuels that can not be used again

describe the ways that people are trying to use technology to protect the environment and increase sustainability.

WILL NAME BRAINLIEST please help

Answers

Answer:

One way people are using technology to protect the environment is:

Using digital devices for communicating and storing information means that there is less reliance on paper, which reduces deforestation. Since trees are an important source of oxygen and also absorb carbon dioxide, this further reduces climate change.

Environmental technology has enabled us to capture this naturally occurring energy and convert it into electricity or useful heat through devices such as solar panels, wind, and water turbines.



Explanation:

Have a great of your day
#TheWizzer

What is simple harmonic oscillation? express your answer verbally, mathematically, and visually.

Answers

Simple harmonic motion is the motion in objects where the restoring for d is directly proportional to the body displacement.

What is simple harmonic motion?

Simple harmonic motion a type of periodic motion where the force that restores moving object to it's right position is directly proportional to the magnitude of body's displacement and this normally acts towards the object's equilibrium position.

The formulate for simple harmonic motion are

,F = −kx, where F is the force, x is the displacement, and k is a constanst. An example of a simple harmonic oscillator is the vibration of a mass attached to a vertical spring.

Simple harmonic oscillator can be represented by the equation x ( t ) = A cos ⁡ ( 2 π f t ) x(t) = A\cos(2\pi f t) x(t)=Acos(2πft)x,

where t is period.

x is displacement

A is amplitude.

Learn more about simple harmonic motion here.

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Please Answer this question

Answers

Answer:

T = 14.7 N

Explanation:

When released the two blocks will accelerate

See diagram below  (hope it is not too confusing or unclear)

1. What is the approximate age of the fossil described in the activity?
1.8 million years
18 million years
.9 million years
90 million years

Answers

Answer:

B.

Explanation:

It should be B. 18 million years ago.


I apologize if it is incorrect-

I hope it helps! Have a great day!

Anygays-

Answer:

B. 18 million years

Explanation:

The answer is B. 18 million years


I hope it helps! Have a great day!

Muffin ^^

Viewed from a distance, how would a flashing red light appear as it fell into a black hole?.

Answers

Explanation:

Light rays that pass close to the black hole get caught and cannot escape. so what ends up happening to the light is that it starts bending due to the strong gravitational force of the black hole.

Please Help Physics!


1. Sound travels through a guitar string at 600 m/s, making a sound wave in the air with a speed of 333 m/s. In 1–2 sentences, explain how the wavelength and frequency of the wave in the string compare to the wavelength and frequency of the wave in the air.

Answers

The wavelength and frequency of the sound in the string is greater than the wavelength and frequency of the sound in the air.

Wavelength and freqeuncy of the sound

The wavelength and frequency of the sound is determined using the following formulas.

v = fλ

f = v/λ

λ = v/f

where;

f is the frequency of the soundλ is the wavelengthWavelength and frequency of the sound in the string

f = 600/λ

λ = 600/f

Wavelength and frequency of the sound in air

f = 333/λ

λ = 333/f

Thus, the wavelength and frequency of the sound in the string is greater than the wavelength and frequency of the sound in the air.

Learn more about wavelength and frequency here: https://brainly.com/question/10728818

A sample of helium behaves as an ideal gas as it is heated at constant pressure from 273 K to 388 K. If 80 J of work is done by the gas during this process, what is the mass of the helium sample? The universal gas constant is 8.31451 J/mol · K. Answer in units of g

Answers

The mass of the helium gas sample after the work is done by the gas during the process is 0.099 g.

Number of moles of the helium gas

The number of moles of the helium gas is calculated as follows;

W = nRT

where;

n is the number of molesW is the work doneR is universal gas constant = 8.31451 J/mol · KT is the final temperature = 388 K

273 K = 0⁰C and 388 K = 115⁰ C

from 0⁰C to 115⁰C = 115 - 0 = 115⁰ C

115⁰ C = 388 K

The number of moles is calculated as follows;

n = W/RT

[tex]n = \frac{80}{8.315 \times 388} \\\\n = 0.0248 \ mol[/tex].

Mass of the helium sample

Mass of the helium sample is calculated as follows;

m = Mn

where;

M is the molar mass of helium gas = 4 g/mol

m = 4 g/mol x 0.0248 mol

m = 0.099 g

Thus, the mass of the helium gas sample after the work is done by the gas during the process is 0.099 g.

Learn more about helium gas here: https://brainly.com/question/3094665

Copper (II) chloride reacts with magnesium nitride

Answers

Answer:

I don't know

Explanation:

because I'm not smart

An astronaut floating alone in outer space throws a baseball. If the ball moves away at 20 m/s, the astronaut will:.

Answers

Answer:

Move the opposite direction ( at a lesser magnitude of velocity)

Explanation:

15 points!! PLEASE ANSWER! I NEED IT QUICK!
What happens to the energy of a wave if the amplitude of the wave is doubled?

How does the frequency of a wave relate to the energy of the wave?

Answers

Answer:

See below ↓

Explanation:

We know that the energy of a wave is directly proportional to the amplitude of a the wave. That means it directly varies, so when one increases/decreases, the other does the same.

Therefore, when the amplitude of a wave is doubled, the energy of the wave is also doubled.

Similarly, in the case of the frequency of the wave, it is also directly proportional to the energy of the wave.

E ∝ ν

What will happen to the period of a ball-on-a-spring if the ball is replaced by a smaller one with half the mass

Answers

When the ball on a spring is replaced by a smaller ball with half the mass :  The period decrease by 29%

Calculate the Period

We will apply the formula below to calculate period

T = [tex]2\pi \sqrt{\frac{m}{k } }[/tex]

 where :

T₁ / T₂ = [tex]\sqrt{\frac{m_{1} }{m_{2} } }[/tex]    where m₂ = m₁ / 2

Therefore :

T₂ = [tex]\frac{T_{1} }{\sqrt{2} }[/tex]   = 0.71 T

Hence we can conclude that the period will decrease by 29% ( i.e 100 - 71 ).

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