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Physics 30 > Unit 6 - Gravitational Fields & The Expanding Universe > Flashcards

Unit 6 - Gravitational Fields & The Expanding Universe Flashcards

1
Q

What does every object on the surface of the earth feel

A

Force of gravity

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2
Q

What exerts gravitational force on its objects

A

The earth itself on its surface

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3
Q

What holds the moon in its orbit

A

The earth

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4
Q

How to describe gravity as a force?

A

It acts at a distance

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5
Q

When is friction exerted?

A

When two objects touch

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6
Q

Newtons quantitative description of gravity

A

Gravity was a field that acted everywhere instantaneously

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7
Q

How did newton believee that the universe could be unsterstood and explained?

A

By studying and describing the behavior of its matter

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8
Q

What do we use to predict today when comets will pass by the Earth, to set satellites in motion around our planet, and also to send astronauts to the moon and someday mars.

A

Newtons dynamics and Keplers laws

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9
Q

What are fields?

A

Fields are regions of influence surround an object. They are invisible and intangible.

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10
Q

What are field models?

A

Used to explain how two objects are exerting (applying) forces on each other without touching. When a second object is placed into this region, this field exerts a force on the object and can cause the object to change motion.

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11
Q

Invented the concept of the field to help explain how a magnet attracts an object. Later the field concept was applied to gravity.

A

Michael Faraday

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12
Q

Anything that has mas is ___

A

Surrounded by a gravitational field

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13
Q

The field that acts on the second body, resulting in ______

A

A force of attraction

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14
Q

What can be used to show the gravitational field surrounding an object with mass?

A

Vectors

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15
Q

What direction is the force of gravity always?

A

Inwards

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16
Q

Zero point

A

A point between the earth and the moon where you would feel no gravitational pull from either celestial body

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17
Q

The radius of the Earth is about __ that of the orbital radius of the moon

A

1/60

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18
Q

The radial acceleration of the moon is about __ that of the acceleration of objects near the surface of the earth

A

1/3600

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19
Q

The gravitational force exerted on any objects by the earth ________ with the _____ of its distance (radius from the earths cenered)

A

decreases
increases

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20
Q

Newton reasoned that the magnitude of the force of gravity must be proportional to ___

A

the mass

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21
Q

What is Newtons law of universal gravitation

A

Every particle in the universe attracts every other particle with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between them. This force acts along the line joining the two particles.

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22
Q

Newtons Law of Universal Gravitation shows that the force of gravity depends on what?

A

Both upon the mass of the two objects and the distance between them

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23
Q

Inverse square law

A

The force of gravity described by Newton is inversely proportional with the square of the distance between the two masses

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24
Q

Henry Cavendish

A

In 1798, experimentally determined the value of G

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25
Where does the earth bulge?
At the equator
26
What place is the closest to the center to the earth?
North and South pole
27
Place that is furthest from the center of the earth
Equator
28
What additionally effects the value of g
The rotation of the earth
29
How is the mass of the earth distributed?
Unevenly
30
What happens if you fire a canonball horizontally at the top of a high mountain?
The cannonball is projectile, and thus it will fall to earth in a parabolic path.
31
If more gunpowder were used in the cannonball, the horizontal component of the projectiles velocity would be ____ The the vertical acceleration would be _____ The parabola would simply become ____
Increased The same Flatter
32
What would happen if Newton’s ball was fired fast enough horizontally?
The ball with fall towards the Earth along the same path as the curvature earth so it will orbit the Earth .
33
The cannonball that is fired horizontally is _____
In a state of free fall
34
What is preventing the cannonball from reaching the earths surface?
It’s horizontal speed
35
What keeps a satellite in orbit?
Centripetal force and force of gravity
36
Describe the motion of satellites
They are accelerating towards the centre of the Earth, but they’re moving horizontally at a speed which prevents them from reaching the surface of the Earth
37
What happens if you are in a state of freefall with no force acting on your feet as you would have standing on the surface of the earth
You feel weightless
38
How are we able to be predict planets orbiting distant stars
The “wobble" of those stars caused by the pull of orbiting planets
39
What allows us to determine the massive things in the universe that we can’t measure directly?
Circular motion
40
What is the mass of the galaxy triangulum using the brightness method equal to?
roughly 5,000,000,000 of our suns mass
41
What is the mass of the triangular galaxy equal to using the orbital method?
Roughly 25 billion
42
Undetectable mass in the universe that does not admit nor absorb, nor does it interact in anyway with the regular matter that we can observe directly
Dark matter
43
What is dark matter made up
Weakly, interacting, massive particles
44
Particles that are not directly observable or detectible so they must be found indirectly throughout the universe
Weakly interacting massive particles
45
Einsteins general theory of relativity
The presence of mass in the universe causes space time to curve. curved space time causes matter to move
46
What does the curvature of space time do?
Causes mass to move and changes the direction of light
47
How does light normally travel?
In a straight line - linear propagation
48
Gravitational lensing
The presence of mass that causes light to change direction
49
What will happen when you look at light from a distance star how will it appear?
It will appear to come from another location than expected from linear propagation
50
What happens when you look at the image of distant galaxies?
The image will be distorted by the presence of large masses from galaxies or dark matter in between
51
What is the percentage of dark matter in the known universe?
23%
52
How is the universe moving?
It is expanding
53
Who invented the telescope and when?
Hans Lippershey in 1608
54
The invention of the telescope related what two principles?
Johannes Keplers three laws of planetary motion and newtons law of universal gravitation
55
Who determined that the Andromeda nebula was actually a separate galaxy from our own
Edwin Hubble
56
How was Edwin Hubble able to determine that the Andromeda galaxy was moving away from us?
By using the Doppler effect (changes colours)
57
Hubble determined using the telescope and redshift (doppler effect) of the stars in different galaxies that the father away that galaxies were from us ____
The faster they were moving away from us
58
What does it mean when it may look like the galaxies are moving away from us?
It is actually space itself that is stretching apart. It is growing bigger— the universe.
59
Who is Alexander Friedman?
A Russian cosmologist who proposed a theoretical, expanding universe by studying Albert Einstein’s general theory of relativity.
60
Who is the Belgian Catholic priest, George LeMaitre?
He proposed that at one time all matter throughout the universe was together in a single location. He theorized that the expansion of the observable universe began with the explosion of a single particle at a definite moment in time.This is known as The Big Bang Theory.
61
Who is Robert Dickie?
He worked out that the Afterglow from the big bang should still be felt to this day
62
What temperature did Dickie and his colleagues calculate the temperature of the empty space should be
3° above absolute zero a.k.a. 3 K/-270°C
63
What did Arno Penzias and Robert Wilson discover?
They were working on a new radio telescope which measured microwaves and radio waves in space in the form of heat and they found that empty space was approximately 5 K/-268°C
64
What is the afterglow of the Big Bang called today?
Cosmic microwave background radiation
65
What does the Hubble space telescope do?
It captures visible light that is unobstructed by the earths atmosphere
66
When images of the universe are captured with the Hubble, not only are you looking out into space but ___
You are also looking back in time
67
What is the Hubble deep field?
Dark empty spot in the night sky that contained billions of galaxies
68
How far did the 2009 images of the Hubble deep field go back in time?
They showed images of galaxies formed only 600,000,000s years after the big bang the time of the birth of the galaxies
69
What is dark energy?
Invisible, undetectable force that is pushing the universe apart with greater magnitude than the force of gravity can pull it together. It causes the universe to accelerate.
70
What is dark energy and what would it do to our universe?
That is a mystery to humanity
71
What percentage is dark energy comprised of in the total universe?
72%
72
What percentage of the entire universe is visible?
5%
73
What is the big crunch?
The universe would once again collapse into a singularity
74
What does the universe being cyclical mean?
It is a sinusoïdal wave in which the period from Big Bang to big crunch is about a trillion years

Physics 30 (3 decks)

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