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aleksklad [387]
3 years ago
5

Spiral galaxy rotation curves are generally fairly flat out to large distances. Suppose that spiral galaxies did not contain dar

k matter. How would their rotation curves be different?(A) The orbital speeds would fall off sharply with increasing distance from the galactic center.(B) The rotation curve would be a straight, upward sloping diagonal line, like the rotation curve of a merry-go-round.(C) The orbital speeds would rise upward with increasing distance from the galactic center, rather than remaining approximately constant.(D) The rotation curve would look the same with or without the presence of dark matter.
Physics
1 answer:
Artemon [7]3 years ago
8 0

Answer:

A) The orbital speeds would fall off sharply with increasing distance from the galactic center.

Explanation:

The plot of radial distance versus the orbital speed of objects gives us the galaxy rotation curve. The theoretical and practical curves have significant difference. A possible explanation of this difference could be the existence of dark matter.

According to the theoretical calculations the curve should increase sharply and then decrease as the radial distance increases. The theoretical graph does not take dark matter into account. But the plot made by observations shows the plot increasing first then becoming constant as the radial distance increases.

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For a top player, a tennis ball may leave the racket on the serve with a speed of 55 m/s (about 120 mi/h). If the ball has a mas
inn [45]

Answer:

Yes is large enough

Explanation:

We need to apply the second Newton's Law to find the solution.

We know that,

F= ma

And we know as well that

a= \frac{v}{t}

Replacing the aceleration value in the equation force we have,

F= \frac{mv}{t}

Substituting our values we have,

F= \frac{(0.060)(55)}{4*10^{-3}}

F=825N

The weight of the person is then,

W = mg

W = (60)(9.8) = 558N

<em>We can conclude that force on the ball is large to lift the ball</em>

6 0
3 years ago
We want to find how much charge is on the electrons in a nickel coin. Follow this method. A nickel coin has a mass of about 4.2
monitta

Answer:

The number of atoms is N = 4.37*10^{22} \ atoms

Explanation:

From the question we are told that

                 The mass of coin  is m_n = 4.2g

                   Number of atom in one mole = n =6.02*10^{23} \ atoms

                   Molar mass of nickel M = 57.8g

Now the relation to obtain the number of atom in  the  nickel coin is

                        N = \frac{Mass \ of Nickel\ coin}{Molar \ mass\ of nickel }  * No\ of\atoms \ in \ \ one\  mole\ of\ nickel

                           = \frac{4.2}{57.8}* 6.02*10^{23}

                           =4.37 *10^{22} atoms

                 

     

8 0
3 years ago
When hydrogen is burned in the presence of oxygen it will form water as per the equation: 2h2
Natasha_Volkova [10]

Answer:

B. In the first case, a combination reaction takes place and in the second case, a decomposition reaction takes place.

Explanation:

When hydrogen burns in oxygen, water is formed and when water is electrolysed then hydrogen and oxygen are produced. What type of a reaction takes place?

(i) In the first case,

(ii) In the second case?

A. In both the cases, i.e. (i) and (ii), a combination reaction takes place.

B. In the first case, a combination reaction takes place and in the second case, a decomposition reaction takes place.

C. In the first case, a combination reaction takes place and in the second case, a displacement reaction takes place.

D. In the first case, a displacement reaction takes place and in the second case, a decomposition reaction takes place.

Answer :

Hint: When hydrogen burns in air, H2H2 reacts with O2O2 to form water molecules. Here two reactants combine to form a single product. And, when water is electrolysed into hydrogen and oxygen, here a single compound decomposes into more than one product.

Complete step by step answer:

In the First case:

When hydrogen burns in oxygen, water is formed.

Hydrogen + Oxygen = Water

2H2+O2→2H2O2H2+O2→2H2O

When two reactants elements combine to form a single component, then this reaction is called the combination reaction. So, in this case, two reactants i.e. Hydrogen and oxygen combine to form a single product i.e. water molecules and heat is also released.

In the Second case:

When water is electrolysed then hydrogen and oxygen are produced.

2H2O→2H2+O22H2O→2H2+O2

When a single reactant is decomposed or broken down into two or more products, it is known as decomposition reaction. Here, a single reactant i.e. water, breaks or decomposes up to form two or more simple products i.e. hydrogen and oxygen. This decomposition reaction takes place by the action of electricity. So, we can see that in the first case, a combination reaction takes place and in the second case, a decomposition reaction takes place.

Therefore, the correct answer is option (B).

Note: Hydrogen is combustible and it burns with a popping sound in oxygen with an almost colourless flame to form water molecules and release heat. This reaction is highly exothermic. Hydrogen must be handled very carefully as the mixture of hydrogen and oxygen can be explosive when two are present in a particular ratio.

7 0
2 years ago
A boy pulls a wagon with an applied force of 40 N on frictionless surface. If the mass of the wagon is 13kg, what is the acceler
Gekata [30.6K]

Answer:

3.1 m/s²

Explanation:

Apply Newton's second law:

∑F = ma

40 N = (13 kg) a

a ≈ 3.1 m/s²

7 0
3 years ago
Which of the following is evidence of Earth's age provided by fossils?
Paladinen [302]
I think the answer is Fossils formed gradually over time.
7 0
3 years ago
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