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iris [78.8K]
3 years ago
6

Listed following are three possible models for the long-term expansion (and possible contraction) of the universe in the absence

of dark energy:
A) recollapsing universe
B) coasting universe
C) critical universe
Rank each model from left to right based on the ratio of its actual mass density to the critical density, from smallest ratio (mass density much smaller than critical density) to largest ratio (mass density much greater than critical density).
Physics
1 answer:
Keith_Richards [23]3 years ago
3 0

Answer:

1. Recollapsing universe

2. Critical universe

3. Coasting universe

Explanation:

Recollapsing universe has dark matter density greater than critical density. While critical universe has its matter density equal to the critical sensity. Coasting universe on the other hand has much smaller matter density compared to critical density.

Note that the critical density is approximately 10^-20 grams/cm3

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Ainat [17]

The great astronomer of ancient times who summarized and improved...in a book now called The Almagest) is Ptolemy This is further explained below.

<h3>Who is Ptolemy?</h3>

Generally, Claudius Ptolemy was a Greek mathematician, astronomer, and geographer who lived in the second century CE and is best known for proposing the geocentric model of the cosmos, which was used to explain planetary and stellar movements for the next thousand years.

In conclusion, Ptolemy, the ancient world's preeminent astronomer, compiled and refined a system of circles inside circles to describe the complexities of planetary motion, publishing his work in what is now known as The Almagest.

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6 0
2 years ago
A penny is dropped from the top of a building that is 300.0 m tall. Calculate the speed of the penny as it hits the ground. (met
Sauron [17]

We have the equation of motion s = ut + \frac{1}{2} at^2, where s is the displacement, a is the acceleration, u is the initial velocity and t is the time taken.

Here s = 300 m, u = 0 m/s, a = 9.81 m/s^2

Substituting

   300 = 0*t+\frac{1}{2} *9.8*t^2\\ \\ 4.9t^2 = 300\\ \\ t =7.82 seconds

Now we have v = u+at, where v is the final velocity

Here u = 0 m/s, a= 9.81 m/s^2 and t = 7.82 seconds

Substituting

     v = 0+9.8*7.82 = 76.68 m/s

The speed with which the penny strikes the ground = 76.68 m/s.

3 0
3 years ago
Glass is transparent to visibile light under normal conditions; however, at extremely high intensities, glass will absorb most o
8_murik_8 [283]

Answer:

3 photons

Explanation:

The energy of a photon E can be calculated using this formula:

E=\frac{hc}{\lambda}

Where h corresponds to Plank constant (6.626070x10^-34Js), c is the speed of light in the vacuum (299792458m/s) and \lambda is the wavelength of the photon(in this case 800nm).

E=\frac{hc}{\lambda}=\frac{(6.626070\times10^{-34})(299792458)}{800\times10^{-9}}=\frac{1.986445812\times10^-25}{800}=2.483057265\times10^{-19}J

Tranform the units

1eV=1.602176634\times10^{-19}J\\2.483057265\times10^{-19}J(\frac{1eV}{1.602176634\times10^{-19}J})=1.549802445eV

The band Gap is 4eV, divide the band gap between the energy of the photon:

\frac{4ev}{1.549802445eV}=2.508974118

Rounding to the next integrer: 3.

Three photons are the minimum to equal or exceed the band gap.

4 0
3 years ago
An endothermic reaction is defined as a reaction that _____.
Dmitry_Shevchenko [17]

Answer:

B.) Releases heat or light

Explanation:

5 0
3 years ago
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In any energy transformation, there is always some energy that gets wasted as non-useful heat.
Nady [450]
It is a completely false statement that in <span>any energy transformation, there is always some energy that gets wasted as non-useful heat. The correct option among the two options that are given in the question is the second option. I hope that this is the answer that has actually come to your desired help.</span>
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3 years ago
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