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3 years ago

If the atomic number of an atom is 4 and the mass number is 9, then how many electrons does it have

1 answer:

5 0

The atomic number of an atom says how many protons it has. This number cant change, since the atomic number is what gives elements their identities (in the periodic table, at least).
The mass number, on the other hand, says how many protons AND neutrons the atom has (so, the sum of P+ and N0). So, electrons have nothing to do with this number.
Atoms are neutrally charged, which means there has to be an equal number of positive and negative particles. The negative particles of an atom are its electrons, and since our atom has 4 protons, it must also have 4 electrons.

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Suppose the balloon is descending with a constant speed of 4.2 m/s when the bag of sand comes loose at a height of 35 m. What is

Margaret [11]

Answer:

2.28 s

Explanation:

Let g = 9.8 m/s2 and neglect air resistance. The box of sand with an initial velocity of 4.2m/s in free fall would yield the following equation of motion

$s = v_0t + gt^2/2$

$35 = 4.2t + 9.8t^2/2$

$4.9t^2 + 4.2t - 35 = 0$

$t= \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$

$t= \frac{-4.2\pm \sqrt{(4.2)^2 - 4*(4.9)*(-35)}}{2*(4.9)}$

$t= \frac{-4.2\pm26.53}{9.8}$

t = 2.28 or t = -3.14

Since t can only be positive we will pick t = 2.28 s

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3 years ago

A change of temperature of 20 C is equivalent to a change in thermodynamic temperature of

Leto [7]

Answer:

20 K

Explanation:

It is given that,

The change in temperature is 20 C.

We need to find the change in thermodynamic temperature.

If teperauture T₁ = 0° C = 0+273 = 273 K

T₂ = 20° C = 20 + 273 = 293 K

The change in temperature,

$\Delta T=T_2-T_1\\\\=293-273\\\\=20\ K$

So, the change in temperature of 20°C is equivalent to 20 K.

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3 years ago

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Law Incorporation [45]

I think this is the answer for the first line(Cooling ,Heating or mixing ) and for the second line is(broken down,cooled,mixed)

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Answer: car b

Explanation:

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3 years ago