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2 years ago

Why are black holes black?

Physics

2 answers:

melomori [17]2 years ago

8 0

Light can't reflect off them I think

Furkat [3]2 years ago

4 0

Black Hole

___________

It is the most mysterious thing in our universe.

✳ John Michell was the first scientist who gave his idea on black hole in 1783

✳ later than Pière simon described black holes in his book the system of the world in 1796.

What are black holes?

=> It is also a celestial body which have infinite gravitational force and infinite mass and even light can not escape from it.

=> If any object goes near a black hole then time slows down for that object.

How black holes formed?

=> Mostly black holes formed because of compression of mass and density of stars.

So, first we know how stars formed and then black holes.

= stars are formed by the cloud of gas and dust present in our universe which we simply called as Nebula.

= They are mostly composed of hydrogen and helium with some amount of another elements.

= when the density of nebula decreases then they contract because of their gravitational force and then its temperature rises at very high level and in that temperature hydrogen atom makes helium by fusion reaction and because of the speed of hydrogen atom and also heat the nebula takes a spherical shape which we call star.

Now black hole formation -

= The gravitational force of stats are balanced by their heat.

And hydrogen acts as a fuel for it.

= and when its hydrogen finishes then with passage of time that star cools down and then its mass and density becomes 4 times greater then its original mass and density.

And then that star can't control its gravitational force and then a blast occurs which we call supernova.

And after this blast if any of the piece of that star which have more mass remains then it becomes a star which have mass and density of a critical level and we call this as Neutron star.

In this type of Neutron star because of its gravitational force then it starts contracting and after contracting it at a critical level then it becomes a body which have infinite density and mass and because of this infinte density and mass the space time bents inward there and then it doesn't be there and we call this as a black hole.

Its whole mass is focused at center which we call it

✳ central singularity point

And the boundary of black hole is called

✳ event horizon

And nothing can escape from here even light can't.

And here concept of time doesn't work.

=> According to theory of relativity if the object is near the black hole then the time slows down for it.

Types of black holes

1. Stellar mass black hole

~> It is the type of black hole formed because of contraction of a star which have mass about 3 times greater than the sun.

2. Super massive black holes

~> It is formed in center of any galaxy and have infinite mass and gravitational force and it has mass about 100000000 times that of sun.

3. Permordial or small black holes

~> They are formed because of the more heat at the center of a star and the mass of that star is less than that of our sun.

Physicist think that they formed with the beginning of universe

✳ the nearest black from earth is

cygnus x1

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If everything with mass is attracted to every other thing with mass, why doesn’t all the matter in the universe pull together in

kupik [55]

Answer:

i need more info

Explanation:

6 0

3 years ago

Read 2 more answers

A ball bearing of radius of 1.5 mm made of iron of density

Serjik [45]

Answer:

$\boxed{\sf Viscosity \ of \ glycerine \ (\eta) = 14.382 \ poise}$

Given:

Radius of ball bearing (r) = 1.5 mm = 0.15 cm

Density of iron (ρ) = 7.85 g/cm³

Density of glycerine (σ) = 1.25 g/cm³

Terminal velocity (v) = 2.25 cm/s

Acceleration due to gravity (g) = 980.6 cm/s²

To Find:

Viscosity of glycerine ( $\sf \eta$ )

Explanation:

$\boxed{ \bold{v = \frac{2}{9} \frac{( {r}^{2} ( \rho - \sigma)g)}{ \eta} }}$

$\sf \implies \eta = \frac{2}{9} \frac{( {r}^{2}( \rho - \sigma)g )}{v}$

Substituting values of r, ρ, σ, v & g in the equation:

$\sf \implies \eta = \frac{2}{9} \frac{( {(0.15)}^{2} \times (7.85 - 1.25) \times 980.6)}{2.25}$

$\sf \implies \eta = \frac{2}{9} \frac{(0.0225 \times 6.6 \times 980.6)}{2.25}$

$\sf \implies \eta = \frac{2}{9} \times \frac{145.6191}{2.25}$

$\sf \implies \eta = \frac{2}{9} \times 64.7196$

$\sf \implies \eta = 2 \times 7.191$

$\sf \implies \eta = 14.382 \: poise$

6 0

3 years ago

I need help witha worksheet over circuitsin physics could someone help??

garik1379 [7]

Yes u can help I need to see th worksheet to help tho

5 0

3 years ago

other than serving as a conduction pathway what is a major function of the pons why is the medulla the most vital part of the br

irga5000 [103]

1. What is the major function of the pons?
-Other than serving as a conduction pathway, the pons also contains a nucleus that is essential for breathing.
2. Why is the medulla the most vital part of the brain?
-Medulla is very important because it function for the involuntary movement and processes that happen in the body without giving a thought about it. It performs crucial tasks like regulating the blood pressure.

3 0

3 years ago

A 0.0250-kg bullet is accelerated from rest to a speed of 550 m/s in a 3.00-kg rifle. The pain of the rifle’s kick is much worse

kondaur [170]

Answer:

a) 4.583 m/s

b) 31.505 J

c) 0.491 m/s

d) 3.375 J

p_player = (110 kg)(8 m/s) = 880 kg m/s

p_ball = (0.41 kg)(25 m/s) = 10.25 kg m/s

Explanation:

HI!

We can calculate the recoil velocity by conservation of momentum, remember that p=mv.

The momentum of the bullet is:

p_b = (0.0250 kg)*(550 m/s )

The momentum of the rifle is:

p_r = (3 kg) * v

Since the total initial momentum is zero:

p_b = p_r

That is:

v = (550 m/s ) (0.0250 kg/ 3 kg ) = 4.583 m/s

The kinetic energy gained by the rifle is:

K = (1/2) m v^2 = (1/2) *(3 kg) *(4.583 m/s)^2 = 31.505 J

We use the same formula as in a), but with m=28kg instead of 3 kg

v = (550 m/s ) (0.0250 kg/ 28 kg ) = 0.491 m/s

Again, the same formula as b, but with m=28 and v=0.491 m/s

K = 3.375 J

p_player = (110 kg)(8 m/s) = 880 kg m/s

p_ball = (0.41 kg)(25 m/s) = 10.25 kg m/s

I believe that the kinetic energy is more related to the problem than the momentum. The relation between these two quantities is:

K = p^2/(2m)

usiing this relation, we get:

K_player = 3520 J

K_ball = 128.125 J

Therefore the kinetic energy of the player is around 27 time larger than the kinetic energy of the ball, that being said, the pain of being tackled by that player is around 27 times greater that being hit by the ball!

4 0

3 years ago