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3 years ago

How many neutrons does element X have if its atomic number is 23 and its mass number is 90?

Physics

2 answers:

givi [52]3 years ago

4 0

Answer:

Explanation:

- The atomic number (Z) of an atom is equal to the number of protons in the nucleus

- The mass number (A) of an atom is equal to the sum of protons and neutrons in the nucleus

Therefore, calling p the number of protons and n the number of neutrons, for element X we have:

Z = p = 23

A = p + n = 90

Substituting p=23 into the second equation, we find the number of neutrons:

n = 90 - p = 90 - 23 = 67

Zina [86]3 years ago

4 0

<h2>Answer:</h2>

<u>The number of neutrons is </u><u>67</u>

<h2>Explanation:</h2>

As we know that the atomic number is the number of protons. If we subtract the atomic number from the mass number, we can actually find the number of neutrons.

Number of neutrons = Mass number - atomic number

Neutrons = 90 - 23 = 67

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n 38 g rifle bullet traveling at 410 m/s buries itself in a 4.2 kg pendulum hanging on a 2.8 m long string, which makes the pend

Kitty [74]

Answer:

68cm

Explanation:

You can solve this problem by using the momentum conservation and energy conservation. By using the conservation of the momentum you get

$p_f=p_i\\mv_1+Mv_2=(m+M)v$

m: mass of the bullet

M: mass of the pendulum

v1: velocity of the bullet = 410m/s

v2: velocity of the pendulum =0m/s

v: velocity of both bullet ad pendulum joint

By replacing you can find v:

$(0.038kg)(410m/s)+0=(0.038kg+4.2kg)v\\\\v=3.67\frac{m}{s}$

this value of v is used as the velocity of the total kinetic energy of the block of pendulum and bullet. This energy equals the potential energy for the maximum height reached by the block:

$E_{fp}=E_{ki}\\\\(m+M)gh=\frac{1}{2}mv^2$

g: 9.8/s^2

h: height

By doing h the subject of the equation and replacing you obtain:

$(0.038kg+4.2kg)(9.8m/s^2)h=\frac{1}{2}(0.038kg+4.2kg)(3.67m/s)^2\\\\h=0.68m$

hence, the heigth is 68cm

4 0

3 years ago

A car has a mass of 1.00 × 103 kilograms, and it has an acceleration of 4.5 meters/second2. What is the net force on the car?

aksik [14]

ANSWER

C. $F=4.5 \times10^3$ . newtons

EXPLANATION

According to Newton's second law,

$F_{net}=ma$ , where

$m=1.00\times 10^3kg$ is the mass measured in kilograms.

and

$a=4.5ms^{2}$ is the acceleration in metres per second square.

We substitute these values to obtain,

$F=1.00\times10^3 \times 4.5$ .

We rearrange to get,

$F=1.00\times4.5 \times10^3$ .

We multiply out the first two numbers and leave our answer in standard form to get,

$F=4.5 \times10^3 N$ .

The correct answer is C

3 0

3 years ago

Which atomic number is the threshold value below which fusion may occur?

Luda [366]

Answer:

The atomic number 26(iron) is the threshold value below which the fusion might occur.

Explanation:

Nuclear fusion is a reaction in which two or more nuclei are combined to form one or more different atomic nuclei and subatomic particles.

Energy released in a fusion reaction is because of a key feature of nuclear matter called the binding energy which is a measure of the efficiency with which its constituent nucleons are bound together.

As we go up in atomic number, the energy released per nuclei goes down until it hits a minimum which is for atomic number 26 (iron) and fusion is not possible.

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3 years ago

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Why is permeable soil best for plants that need a lot of drainage? Water fills this type of soil. Water dries up in this type of

Sergeu [11.5K]

Answer:

Water flows through this type of soil.

Explanation:

By definition permeable soil is soil which water and other fluid flow easily through (like sand) If a plant needs drainage the soil will need to flow through the soil easily.

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loris [4]

Answer:

Pish posh idk xD im busy but ill help in a second

Explanation:

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3 years ago