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3 years ago

Potassium’s atomic number is 19, and its atomic mass is approximately 39. How many neutrons does potassium have?

Physics

2 answers:

yarga [219]3 years ago

6 0

Answer:

Explanation:

Atomic number is same as the number of protons of an atom and atomic mass is equal to the sum of number of protons and number of neutrons of an atom.

Atomic number = 19

So, number of protons (p) = 19

Atomic mass = 39

So, sum of number of neutrons and number of protons (n + p) = 39

Number of neutons (n)

= (n + p) - p

= 39 - 19

= 20

Andrej [43]3 years ago

5 0

Answer:

Explanation:

The atomic mass is the sum of the number of protons and the number of neutrons, and also, the atomic number is the number of protons, so:

19 + number of neutrons = 39

number of neutrons = 39 – 19

number of neutrons = 20

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An automobile starter motor has an equivalent resistance of 0.0510 Ω and is supplied by a 12.0 V battery with a 0.0090 Ω interna

Alisiya [41]

Answer:

a) 200A

b) 10.2V

c) 2.04kW

I=80A

V=4.08V

P=0.326kW

Explanation:

Here we have a circuit of one power source and two resistors in series, the first question is asking for the current, so according to Ohm's Law:

$I=\frac{V}{R}$

Where R is the equivalent resistance of the resistors in series

$R=0.0510+0.0090=0.0600[ohm]$

$I=\frac{12.0}{0.0600}=200A$

To calculate the voltage dropped by the motor we have to apply the voltage divider rule:

$V_m=V*\frac{R_m}{R_m+R_s}\\V_m=12.0*\frac{0.0510}{0.0600}\\V_m=10.2V$

The power dissipated supplied to the motor is given by:

$P=I^2*R_m\\P=(200)^2*0.0510=2.04kW$

now solving adding a 0.0900 ohm resistor:

$I=\frac{12.0}{0.15}=80A$

$V_m=12.0*\frac{0.0510}{0.15}\\V_m=4.08V$

$P=I^2*R_m\\P=(200)^2*0.0510=0.326kW$

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3 years ago

What are the three main categories of elements?

o-na [289]

Answer:

Classification of the Elements. These three groups are: metals, nonmetals, and inert gases.

Explanation:

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3 years ago

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Which of these instruments can be used to peedict a thunderstorm?

FinnZ [79.3K]

<span> Doppler Radar is the instrument that is used to predict a thunderstorm. </span>

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3 years ago

Select three different examples of accelerated motion. a body traveling in a straight line and increasing in speed a body travel

IrinaVladis [17]

This is the same question that I just answered.

Have present the definition of acceleration:

a = Δv / Δt, this is change in velocity per unit of time.

a and v are in bold to mean that they are vectors.

1) a body traveling in a straight line and increasing in speed: CORRECT:

Acceleration is the change in velocity, either magnitude or direction or both. So, a body increasing in speed is accelerated.

2) a body traveling in a straight line and decreasing in speed: CORRECT

A decrease in speed is a change in velocity, so it means acceleration.

3) a body traveling in a straight line at constant speed: FALSE.

That body is not changing either direction or speed so its motion is not accelerated but uniform.

4) a body standing still : FALSE.

That body is not changind either direction or speed.

5) a body traveling at a constant speed and changing direction: CORRECT.

The change in direction means that the body is accelerated. The acceleration due to change in direction is named centripetal acceleration.

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4 years ago

A person observing a flame is interested in the types of electromagnetic waves with slightly shorter and slightly longer wavelen

Nadya [2.5K]

Answer:

Ultra violet rays and infrared rays

Explanation:

The electromagnetic radiation in the order of increasing wavelength is given as

Gamma rays

X rays

Ultra violet rays

Visible radiation

Infrared rays

Microwaves

radiowaves

So, the radiations having wavelength more than the visible radiation are infrared radiations and the radiations which having the wavelength less then the visible radiation is Ultraviolet rays.

So, we observe ultra violet radiations and infrared radiations.

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4 years ago