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vovangra [49]
3 years ago
10

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

Physics
1 answer:
miskamm [114]3 years ago
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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A tree loses water to the air by the process of transpiration at the rate of 110 g/h. This water is replaced by the upward flow
Ksivusya [100]

Answer:

The answer is 1.87nm/s.

Explanation:

The 110g/hr  water loss must be replaced by 110g/hr of sap. 110g of sap corresponds to a volume of  

110g \div \dfrac{1040*10^3g}{1*10^6cm^3}  = 106cm^3

thus rate of sap replacement is

106cm^3/hr = 106*10^{-6}m^3/3600s  = 2.94*10^{-8}m^3/s

The volume of sap in the vessel of length x is

V = Ax,

where A is the cross sectional area of the vessel.

For 2000 such vessels, the volume is

V = 2000Ax

taking the derivative of both sides we get:

\dfrac{dV}{dt} = 2000A \dfrac{dx}{dt}

on the left-hand-side \dfrac{dx}{dt} is the velocity v of the sap, and on right-hand-side \dfrac{dV}{dt}  = 2.94*10^{-8}m^3/s; therefore,

2.94*10^{-8}m^3/s=2000Av

and since the cross-sectional area is

A = \pi (\dfrac{100*10^{-3}m}{2} )^2 = 7.85*10^{-3}m^2;

therefore,

2.94*10^{-8}m^3/s =2000(7.85*10^{-3}m^2)v

solving for v we get:

v = \dfrac{2.94*10^{-8}m^3/s}{2000(7.85*10^{-3}m^2)}

\boxed{v =1.875*10^{-9}m/s = 1.875nm/s}

which is the upward speed of the sap in each vessel.

8 0
3 years ago
What is the scientific name given to potato​
Burka [1]
The answer: Solanum tuberosum
8 0
3 years ago
Read 2 more answers
The magnitude of a force is:
lys-0071 [83]

Answer:

c

Explanation:

force is how hard it is pulled or pushed

3 0
3 years ago
Compute the velocity of an electron that has been accelerated through a difference of potential of 100 volts. express your answe
Elodia [21]

The velocity of an electron that has been accelerated through a difference of potential of 100 volts will be 5.93 * 10^{6} m/s

Electrons move because they get pushed by some external force. There are several energy sources that can force electrons to move. Voltage is the amount of push or pressure that is being applied to the electrons.

By conservation of energy, the kinetic energy has to equal the change in potential energy, so KE=q*V. The energy of the electron in electron-volts is numerically the same as the voltage between the plates.

given

charge of electron = 1.6 × 10^{-19} C

mass of electron  = 9.1 × 10^{-31} kg

Force in an electric field = q*E

potential energy is stored in the form of work done

potential energy = work done = Force * displacement

                                                   = q * (E * d)  

                                                   = q * (V) = 1.6 × 10^{-19} * 100

stored potential energy = kinetic energy in electric field

kinetic energy = 1/2 * m * v^{2}

                        = 1/2 *  9.1 × 10^{-31} *  v^{2}

equation both the equations

1/2 *  9.1 × 10^{-31} *  v^{2} = 1.6 × 10^{-17}

v^{2} = 0.352 * 10^{14} m/s

v^{2} = 35.2 * 10^{12}

    = 5.93 * 10^{6} m/s

To learn more about  kinetic energy in electric field  here

brainly.com/question/8666051

#SPJ4

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1 year ago
An X-Ray machine delivers a radiation dose of 5mRem/hr. at 3ft from the machine. How far will the X-Ray technician have to move
kupik [55]

Answer:

4.7ft

Explanation:

Pls see attached file

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