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2 years ago

4. The chart shows melting and boiling points of

Physics

1 answer:

kondor19780726 [428]2 years ago

6 0

Answer:

The correct option is A

Explanation:

Firstly, it should be noted that the freezing point of a substance can be assumed to be melting point of that substance because a substance will normally change from liquid to solid (freezes) at the same point it changes from solid to liquid (melts). For example, water freezes at 0°C and also starts melting at 0°C.

Thus, the substance with the lowest melting point among the substances mentioned in the question is alcohol (ethanol) with the melting point of -114°C. Hence, <u>ethanol also has the lowest freezing point thereby freezing at the lowest temperature.</u>

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Enter your answer in the provided box. The mathematical equation for studying the photoelectric effect is hν = W + 1 2 meu2 wher

siniylev [52]

Answer:

$v = 4.44 \times 10^5 m/s$

Explanation:

By Einstein's Equation of photoelectric effect we know that

$h\nu = W + \frac{1}{2}mv^2$

here we know that

$h\nu$ = energy of the photons incident on the metal

$W$ = minimum energy required to remove photons from metal

$\frac{1}{2}mv^2$ = kinetic energy of the electrons ejected out of the plate

now we know that it requires 351 nm wavelength of photons to just eject out the electrons

so we can say

$W = \frac{hc}{351 nm}$

here we know that

$hc = 1242 eV-nm$

now we have

$W = \frac{1242}{351} = 3.54 eV$

now by energy equation above when photon of 303 nm incident on the surface

$\frac{1242 eV-nm}{303 nm} = 3.54 eV + \frac{1}{2}(9.1 \times 10^{-31})v^2$

$4.1 eV = 3.54 eV + (4.55 \times 10^{-31}) v^2$

$(4.1 - 3.54)\times 1.6 \times 10^{-19}) = (4.55 \times 10^{-31}) v^2$

$8.96 \times 10^{-20} = (4.55 \times 10^{-31}) v^2$

$v = 4.44 \times 10^5 m/s$

6 0

3 years ago

Which classification scheme is based on the brightness of a star as it appears to you in the night sky?

anastassius [24]

The apparent magnitude scale is a classification scheme which is based on the brightness of stars. The range of brightness values is from 1 to 6.
The stars which are the most brightest are ranked as number 1 and also called first magnitude stars, stars which are little dimmer than number 1 are ranked as number 2 and also called second magnitude stars. Similarly the most faintest stars are ranked number 6 and also called as the sixth magnitude stars.

3 0

3 years ago

Eli states that sodium phosphate is a mixture because it is composed of both sodium ions and phosphate ions.

galina1969 [7]

The question is incomplete, the complete question is;

Eli states that sodium phosphate is a mixture because it is composed of both sodium ions and phosphate ions. Which is the best analysis of Eli’s statement? It is correct because each ion is a pure substance, so sodium phosphate is made up of two pure substances. It is correct because the composition of sodium phosphate changes depending on the sample. It is incorrect because sodium phosphate is a compound that has a single composition. It is incorrect because the two types of ions in sodium phosphate cannot be seen.

Answer:

It is incorrect because sodium phosphate is a compound that has a single composition

Explanation:

A compound is a neutral substance made up of two or more atoms which are chemically combined together.

Ionic substances are made up of ions. These ions are not separate entities, they are part of the compound.

Hence, Eli's statement is incorrect because sodium phosphate is a compound that has a single composition.

5 0

3 years ago

How can the momentum of an object be changed?

pickupchik [31]

C. You’re welcome

Leave a like

3 0

3 years ago

Two parallel plate capacitors 1 and 2 are identical except that capacitor 1 has charge +q on one plate and charge −q on the othe

Grace [21]

Answer:

a) the capacitance is the same for both capacitors.

b) The potential difference between the plates for the capacitor with charge +2q, is double of the one for the capacitor with charge +q.

c) The electric field magnitude between the plates for the capacitor with charge +2q, is double of the one for the capacitor with charge +q

d) The energy stored between the plates for the capacitor with charge +2q, is 4 times the value for the one with charge +q

Explanation:

a) The capacitance of a capacitor, by definition, is as follows:

$C = \frac{q}{V}$

Appying Gauss' Law to one of plates, it can be showed, that the capacitance (for a parallel plates capacitor) can be expressed as follows:

C = ε*A / d

As it can be seen, it does not depend on the charge. so we conclude that the capacitance must be the same for both capacitors, due to they are identical except for the value of the charge on the plates.

b) By definition, as we said above, the capacitance is equal to the proportion between the charge of one of the plates, and the potential difference between them.

If this proportion must remain the same, and one of the capacitors has the double of the charge than the other, the potential difference must be the double also.

c) Applying Gauss' law, to the surface of one of the plates, and assuming a constant surface charge density σ, it can be showed that the electric field can be calculated as follows:

E*A = Q/ε₀ as σ=Q/A

⇒ E = σ/ε₀

As σ is directly proportional to the charge (being the area A the same), we conclude that the electric field for the capacitor with charge +2q must be the double than the one for the capacitior with charge +q.

c) The electric potential energy, stored between plates of a capacitor, can be written as follows:

$Ue = \frac{1}{2} *\frac{q^{2}}{C}$

If the capacitance remains the same, we can conclude that the electric potential energy for the capacitor with charge +2q, as the charge is raised to the 2nd power, must be 4 times the one for the capacitor with charge +q.

4 0

3 years ago