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Sonja [21]
3 years ago
13

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

of dark energy. 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).
(A) coasting universe
(B) critical universe
(C) recollapsing universe
Physics
1 answer:
Lynna [10]3 years ago
6 0

Answer:

1) Recollapsing universe

2) critical universe

3) Coasting universe

Explanation:

According to the smallest ration (ratio actual mass density to current density) to largest ration, rank of models for expansion of universe are

1) Recollapsing universe -in this, metric expansion of space is reverse and universe recollapses.

2) critical universe - in this, expansion of universe is very low.

3) Coasting universe -  in this, expansion of universe is steady and uniform

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A tennis player swings her 1000 g racket with a speed of 10 m/s. She hits a 60 g tennis ball that was approaching her at a speed
Mashutka [201]

(a)

consider the motion of the tennis ball. lets assume the velocity of the tennis ball going towards the racket as positive and velocity of tennis ball going away from the racket as negative.

m = mass of the tennis ball = 60 g = 0.060 kg

v₀ = initial velocity of the tennis ball before being hit by racket = 20 m/s

v = final velocity of the tennis ball after being hit by racket = - 39 m/s

ΔP = change in momentum of the ball

change in momentum of the ball is given as

ΔP = m (v - v₀)

inserting the above values

ΔP = (0.060) (- 39 - 20)

ΔP = - 3.54 kgm/s

hence , magnitude of change in momentum : 3.54 kgm/s

7 0
2 years ago
A doctor has a patient blow on one side of a U-shaped tube that is partially
mart [117]

Answer:

A. 150 Pa

Explanation:

Answer is 150 Pa

8 0
3 years ago
Can an object in motion ever change directions?
choli [55]

Answer:

Forces affect how objects move. They may cause motion; they may also slow, stop, or change the direction of motion of an object that is already moving. Since force cause changes in the speed or direction of an object, we can say that forces cause changes in velocity.

4 0
3 years ago
This problem will require you to make some assumptions, so be sure that your assumptions are clear. You have dinner reservations
sertanlavr [38]

Answer:

No

Explanation:

The statement is implying that if you do a certain amount of work, you're entitled to do a certain amount of work. Sometimes, work doesn't entitle you a reward.  

6 0
3 years ago
At the very end of Wagner's series of operas The Ring of Nibelung, Brunnhilde takes the golden ring form the finger of the dead
Blababa [14]

Answer:

a) 404 m² b) apparent height = 7.5 m

Explanation:

This question is about refraction and total internal refraction.

Here I will take refractive index of air and water

n_{air}=1\\ n_{water}=1.33=4/3

Now let's look at the diagram I have attached here

At some angle A, the light from the ring (yellow point) under water will be totally internally refracted (B = 90°), which means that rays of light (yellow arrow) that make large enough angle A will not be able to escape from the water. Since we assumed that the ring is a point, there will be a critical cone of angle A with the ring at its apex which traces a circle of radius R on the surface of water, which, beyond this radius, no light could escape.

According to snell's law

\frac{sin(B)}{sin(A)} = \frac{n_{water}}{n_{air}} = 4/3

At critical angle B = 90°

\frac{3)}{4}sin(B) = [tex]\frac{3}{4} sin(90^\circ ) = 0.75 = sin(A)

Therefore

A = 48.6^\circ

With this, we can find the radius of the circle (refer to my diagram)

h* tan (A) = R\\R =11.3 m

And with that we can find the area

A = \pi R^2=404\ m^2

Additional Problem

For apparent depth from above, we can think that, since we are accustomed to seeing light at the speed of c in air, our brain interpret light from <em>any</em> source to be traveling at c. This causes light that originated under water, which has the speed of

v_{water} = \frac{c}{n_{water}} = 0.75c

to appear as if it has traveled with the same duration as light with speed c

In order for this to happen our brain perceive shortened length  which is the apparent depth.

To put it in mathematical term

t_{travel}=\frac{h_{apparent}}{v_{water}} =\frac{h}{c}

So we get apparent depth

h_{apparent}=0.75h = 7.5\ m

4 0
3 years ago
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