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4 years ago

We determine the distance of a Cepheid in another galaxy by

Physics

1 answer:

Triss [41]4 years ago

5 0

Answer:

We determine the distance of a Cepheid in another galaxy by <em>b) determining its luminosity from the period-luminosity relation and then applying the inverse square law.</em>

<em>Explanation:</em>

Cepheid stars are stars that periodically brighten up or dim. This kind of behaviour allows them to be used as cosmic yardsticks out to a distance of a few tens of millions of light-years. The continuous luminosity variations in these stars allows their period to be measured accurately.

The astronomer Henrietta Levitt discovered that there is a relationship between a Cepheid's brightness and its' pulsation period. This relation was used to measure distances to nearby galaxies. The brighter the star, the longer the period.

The inverse square law for light describes that the intensity of light is inversely proportional to the squared distance of the source. This means that as the distance increases, the intensity of the light decreases. The mathematical expression is:

I ∝ 1 / d²

where

d is the distance

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Mnenie [13.5K]

The last choice on the list is the correct one, for both #2 and #3.

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4 years ago

A mass is oscillating horizontally on a spring. At the locations A, B, C, D, and E, photogates are used to measure the speed of

svetoff [14.1K]

Complete Question

The complete question is is shown on the first uploaded

Answer:

The elastic potential energy at point B is $PE_{elastic} = 50J$

The kinetic energy at point D is $KE = 75J$

Explanation:

Looking at the given point we can observe that mechanically energy(i.e potential and kinetic energy ) is conserved and it value is $E_ {m} = 100J$

So at point B

$E_{m} = PE_{elastic} +KE$

$100 = PE_{elastic} + KE$

KE at point B is 50J

So $PE_{elastic} = 100 - 50 = 50J$

Now at point D

$E_{m} = PE_{elastic} +KE$

$PE_{elastic}$ at point D is 25J

So $KE = 100 - 25 = 75J$

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3 years ago

What is the difference between a neutralization reaction and a double-displacement reaction? (1 point) Double-displacement react

Alchen [17]

Answer:

Neutralization reactions always produce water and a salt.

Explanation:

There are different types of chemical reactions that occurs. Two of them are neutralization and double-displacement reaction. Neutralization reaction is the reaction between an acid and a base to give an acid salt and water as products. For example:

2NaOH (base) + H2SO4 (acid) → Na2SO4 (salt) + 2H2O (water)

On the other hand, Double displacement reaction is the reaction that involves an ion exchange between the reactants to form new products. This ionic exchange occurs in such a way that two reactants form two new products. For example:

2NaCl + Ca(NO3)2 → CaCl2 + 2NaNO3

Therefore, the major difference between these two types of reactions is that: NEUTRALIZATION MUST ALWAYS PRODUCE WATER AND SALT AS PRODUCTS.

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3 years ago

A straight wire of length 0.62 m carries a conventional current of 0.7 amperes. What is the magnitude of the magnetic field made

anyanavicka [17]

Answer:

Magnetic field at point having a distance of 2 cm from wire is 6.99 x 10⁻⁶ T

Explanation:

Magnetic field due to finite straight wire at a point perpendicular to the wire is given by the relation :

$B=\frac{\mu_{0}I }{2\pi R }\times\frac{L}{\sqrt{L^{2}+R^{2} } }$ ......(1)

Here I is current in the wire, L is the length of the wire, R is the distance of the point from the wire and μ₀ is vacuum permeability constant.

In this problem,

Current, I = 0.7 A

Length of wire, L = 0.62 m

Distance of point from wire, R = 2 cm = 2 x 10⁻² m = 0.02 m

Vacuum permeability, μ₀ = 4π x 10⁻⁷ H/m

Substitute these values in equation (1).

$B=\frac{4\pi\times10^{-7}\times 0.7 }{2\pi \times0.02 }\times\frac{0.62}{\sqrt{(0.62)^{2}+(0.02) ^{2} } }$

B = 6.99 x 10⁻⁶ T

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3 years ago

Please help! What is physical property and what is chemical property?

sladkih [1.3K]

PHysical properties are properties that do not involve changes in the molecular level. In this case, malleability and magnetism are physical.
Chemical properties involve changes to the substance at the molecular level or change its identity. In this case, reacting with oxygen and nonflammability is a chemical property.

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4 years ago