A person is talking in a small room and the sound intensity level is 60 dB everywhere within the room. If there are eight people talking simultaneously in the room, what is the sound intensity level?


Answer 1




For a single person the intensisty is and the sound intensity level in decibels , to relate this two we use the equation:

where is a constant: , and since

We have 8 people, so the intensity now is 8 times the intensity of a single person:

and the new sound intensity that I will call will be:

and due to the property of the logarithm of a product:

The first part of the right side of the equation, is the equation we found at the  beginning:

so we substitute this value and we have:

The sound intensity level due to 8 people is 69db

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Curious Carl and his lab partner were burning various fuels; sucrose, paper, and methane, in oxygen and predicting the products. Assuming sufficient oxygen and complete combustion, each combustion reaction produced


Answer: carbon dioxide and water


Fossil fuels are fuels formed in the earth from plant or animal remains. It is mostly composed of coal, natural gas and petroleum.

Combustion is a type of chemical reaction in which fuel is reacted with oxygen to form carbon dioxide and water.

As all the given substances contain carbon and hydrogen as its constituents, all will form carbon dioxide and water on reacting with oxygen.

Example: Combustion of methane

c. water and carbon dioxide .


A California geothermal power plant generates 4.3 MW by extracting 24 MW of heat from an underground source at 108°C and then discharging waste heat into the 17°C air. What is the actual efficiency of the plant?

What is the theoretical efficiency?




Power generated,P_0 = 4.3 MW

Power extracted = 24 MW

Temperature of source,T₁ = 108°C

Temperature of discharge,T₂ =  17°C

a) Actual efficiency




b) Maximum theoretical efficiency





A gas mixture contains 320mg methane, 175 mg argon, 225 mg nitrogen (N2). The partial pressure of argon at 300K is 12.52 kPa. What is the volume and total pressure of the mixture?


Answer: The volume and total pressure of the mixture is 0.876 L and 89.36 kPa respectively.


To calculate the number of moles, we use the equation:


  • For methane:

Given mass of methane = 320 mg = 0.3 g     (Conversion factor:  1 g = 1000 mg)

Molar mass of methane = 16 g/mol

Putting values in equation 1, we get:

  • For argon:

Given mass of argon = 175 mg = 0.175 g

Molar mass of argon = 40 g/mol

Putting values in equation 1, we get:

  • For nitrogen:

Given mass of nitrogen = 225 mg = 0.225 g

Molar mass of nitrogen = 28 g/mol

Putting values in equation 1, we get:

To calculate the volume of the mixture, we use the equation:

PV = nRT         ......(2)

We are given:

Partial pressure of argon = 12.52 kPa

Temperature = 300 K

R = Gas constant =

n = number of moles of argon = 0.0044 moles

Putting values in equation 2, we get:

Now, calculating the total pressure of the mixture by using equation 2:

Total number of moles = [0.019 + 0.0044 + 0.0080] mol = 0.0314 mol

V= volume of the mixture = 0.876 L

Putting values in equation 2, we get:

Hence, the volume and total pressure of the mixture is 0.876 L and 89.36 kPa respectively.


Apa dimensi besaran pokok ..?


Apakah anda berbicara dalam bahasa Indonesia?

What language is this


  The diagram shows a tray of marbles being shaken from side to side.  As this happens some of the marbles jump out of the tray. Explain how the tray of marbles is acting as a model for the evaporation of a liquid.


When the tray of marbles are shaken, the marbles detaches from each other and gains energy to jump out. In a similar way, the liquid particles will escapes to vapor phase when they attain sufficient energy.

What is evaporation ?

Evaporation is the the physical transition of  a substance from its liquid state to vapor state. The temperature at which a substance changes from its liquid state to gaseous state where the vapor pressure of gas above the liquid phase is equal to atmospheric pressure is called its boiling point.

To boil or evaporate a substance, sufficient heat energy have to  be applied to weaken the intermolecular forces between the liquid particles. Thus, by absorbing heat energy, the molecules gains kinetic energy to move apart which in turn results in weakening of intermolecular force.

Here, the marbles jumps out of the tray by gaining some kinetic energy. Similar way the liquid particles overcome the barrier potential and escape to the vapor phase.

Find more on evaporation:


The marbles that are 'more energetic' fall out of the tray, in the same way particles have enough energy to escape and turn into a gas.

A photon with a frequency of 5.48 × 10^14 hertz is emitted when an electron in a mercury atom falls to a lower energy level.

Calculate the energy of this photon in joules. [Show all work, including the equation and substitution with


The energy of the photon in joules, given that it's has a frequency of 5.48×10¹⁴ Hz is 36.33×10¯²⁰ J

Data obtained from the question
  • Frequency (f) = 5.48×10¹⁴ Hz
  • Energy (E) =?

How to determine the energy
  • Planck's constant (h) = 6.63×10¯³⁴ Js
  • Frequency (f) = 5.48×10¹⁴ Hz
  • Energy (E) =?

The energy of the photon can be obtained as follow:

E = hf

E = 6.63×10¯³⁴ × 5.48×10¹⁴

E = 36.33×10¯²⁰ J

Learn more about energy:


     Using the Planck's Equation, comes:

If you notice any mistake in my english, please let me know, because i am not native.

A 1000 kg car moves as speed from 10 m/s to 30 m/s in 20 seconds. What is the average speed ? What is the acceleration ? What is the average force acting upon it ? If the car turns along a circle at speed 5 m/s around a curve 30 meters in radius , how big the centripetal force is needed ?


Answer: divide



What are three well known American mountains


The Statue of liberty, Mount rushmore, Washington monument, Fort Mchenry are some examples of american monuments.

Appalachian mountains, sierra Nevada, and rocky


The human male gamete is called a sperm cell and is produced in the a. ovaries.
b. spleen.
c. liver.
d. testes.


The human male gamete is called a sperm cell and is produced in the testies. (d).

The correct answer is D. testes, weird question lol.

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