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3 years ago

Who was the man who lived from 460B.C.–370B.C. and was among the first to suggest the idea of atoms?

1 answer:

6 0

C. Democritus was a Greek philosopher who defined the concept of atoms and is the only one of the answer choices who lived during that time period.

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A student discovers that sound waves travel 1,687.5 meters in 5 seconds through air at a temperature of 10°C. Based on this info

vitfil [10]

Answer:

The speed of sound, in m/s, through air at this temperature is 343.5 m/s

Explanation:

Given;

distance traveled by sound, d = 1,687.5 meters

time taken for the sound to travel, t = 5 seconds

air temperature, θ = 10°C

Speed of sound = distance traveled by sound / time taken for the sound to travel

Speed of sound = d / t

= 1687.5 m / 5 s

= 337.5 m/s

Speed of sound at the given temperature is calculated as;

c = 337.5 + 0.6θ

c = 337.5 + 0.6 x 10

c = 337.5 + 6

c = 343.5 m/s

Therefore, the speed of sound, in m/s, through air at this temperature is 343.5 m/s

8 0

3 years ago

The first and second coils have the same length, and the third and fourth coils have the same length. They differ only in the cr

stealth61 [152]

Answer:

$\frac{R_2}{R_1}=\frac{A_1}{A_2}\\\frac{R_4}{R_3}=\frac{A_3}{A_4}$

Explanation:

The resistance of a conductor is directly proportional to its length and is inversely proportional to its cross-sectional area, this dependence is given by:

$R=\frac{\rho L}{A}$

$\rho$ is the material's resistance, L is the legth and A is the cross-sectional area.

For the first and second coils, we have:

$R_1=\frac{\rho L}{A_1}\\R_2=\frac{\rho L}{A_2}\\\rho L=R_1A_1\\\rho L=R_2A_2\\R_1A_1=R_2A_2\\\frac{R_2}{R_1}=\frac{A_1}{A_2}$

For the third and fourth coils, we have:

$R_3=\frac{\rho L'}{A_3}\\R_4=\frac{\rho L'}{A_4}\\\rho L'=R_3A_3\\\rho L'=R_4A_4\\R_3A_3=R_4A_4\\\frac{R_4}{R_3}=\frac{A_3}{A_4}$

6 0

3 years ago

Describe how the number of photoelectrons emitted from a metal plate in the photoelectric effect would change if the following o

andrew-mc [135]

Answer:

a) True. The number of photoelectrons is proportional to the amount (intensity) of the incident beam. From the expression above we see that threshold frequency cannot emit electrons.

b) λ = c / f

Therefore, as the wavelength increases, the frequency decreases and therefore the energy of the photoelectrons emitted,

c) threshold energy

h f =Ф

Explanation:

It's photoelectric effect was fully explained by Einstein by the expression

Knox = h f - fi

Where K is the kinetic energy of the photoelectrons, f the frequency of the incident radiation and fi the work function of the metal

a) True. The number of photoelectrons is proportional to the amount (intensity) of the incident beam. From the expression above we see that threshold frequency cannot emit electrons.

b) wavelength is related to frequency

λ = c / f

Therefore, as the wavelength increases, the frequency decreases and therefore the energy of the photoelectrons emitted, so there is a wavelength from which electrons cannot be removed from the metal.

c) As the work increases, more frequency radiation is needed to remove the electrons, because there is a threshold energy

h f =Ф

7 0

3 years ago

How are humans potentially vulnerable to some of these same chemicals? How are humans potentially vulnerable to some of these sa

Svetradugi [14.3K]

The 5 major unit processes include chemical coagulation, flocculation, sedimentation, filtration, and disinfection (described below). There are chemicals added to the water as it enters the various treatment processes.

6 0

2 years ago

The frequency of a certain sound is 440 Mz. What is the wavelength of this sound when the temperature of the air is (a) 20°C; (b

Serggg [28]

Answer:

Explanation:

We know the frequency and the velocity, both of which have good units. All we have to do is rearrange the equation and solve for

Let's plug in our given values and see what we get!

340

440

−

0.773

3 0

2 years ago