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PHYSICS > CHAPTER 16 > Flashcards

CHAPTER 16 Flashcards

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1
Q

what is a comet

A

a lump of frozen rock that orbits the sun

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2
Q

what are meteors

A

rocks that burn up when they enter the earths atmosphere

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3
Q

why do you only see comets when they are near the sun

A

they heat up so much that they emit light

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4
Q

the shape of the orbit of a comet

A

elliptical

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5
Q

how did the sun form

A

clouds of dust and gas were pulled together by gravitational attraction

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6
Q

how was the solar system formed

A

the heat from the sun drove the gas in the atmosphere away creating rocks planets close to the sun

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7
Q

what is a protostar

A

a star to be

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8
Q

how is a protostar formed

A

the clouds of particles are pulled together by forces of attraction so they speed up and collide with more force. this merges the clouds together and a protostar formed

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9
Q

describe the process by which a protostar turns into a star

A

a protostar becomes denser meaning the particles have more energy and speed up increasing the temperature
if the protostar becomes hot enough hydrogen nuclei fuse and form a helium nuclei this releases huge amounts of energy which make the star shine

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10
Q

where is energy transferred from/to in the formation of a star

A

gravitational energy store to thermal energy store

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11
Q

what happens to object formed that are too small to become stars

A

they turn into planets orbiting the star

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12
Q

what is a main sequence star

A

it is in the middle of the long, stable period which is the main stage in the life of a star

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13
Q

how long does the stable period last

A

normally several billon years

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14
Q

what is the heaviest known natural element

A

uranium

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15
Q

half life of uranium

A

4.5 billion years

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16
Q

what makes a star stable

A

when the outward force of fusion trying to expand the star and the force of gravity pulling everything inwards are balanced

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17
Q

when does the stable period of a star end

A

when most of the hydrogen nuclei have fused to form helium nuclei

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18
Q

why can a comet not be seen when it is far away from the sun

A

doesn’t absorb enough energy to burn

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19
Q

one difference between a comet and an asteroid

A

asteroids are made of rocky material and metals but comets are made of ice dust and rocky material

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20
Q

one similarity between a comet and an asteroid

A

both orbit the sun

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21
Q

largest planet in the solar system

A

Jupiter

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22
Q

planet nearest the sun

A

mercury

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23
Q

why is earth likely to be the only planet where liquid can exist

A

its position in the solar system means it has a temperature between 0 and 100 degrees - the conditions needed for liquid water

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24
Q

why is uranium evidence that the solar system must have formed from a supernova

A

they can make other heavier elements by bombarding uranium with neutrons which would have been found in the supernova

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25
what type of star is thesun
a red giant
26
what happens to stars when fusion begins to slow down
it beings to swell out into a red giant or supergiant the surface turns red as it cools down
27
why does the surface of a star turn red
it is cooling down
28
what happens when a star turns into a red giant
elements such as helium fuse and heavier elements up to iron are formed in the core
29
what does a red giant eventually turn into
a white dwarf
30
how does a red giant become a white dwark
it becomes unstable as no more radiation is released gravity forces the star to collapse in on itself this core heats as it collapses turning it from red to white
31
how does a white dwarf turn into a black dark
they cool down and release less energy once it stops releasing a significant amount it turns black
32
what happens to larger stars after their long stable period end
they swell to become a red supergiant
33
what is the next stage after being a red supergiant
supernova
34
how does a red supergiant turn into a supernova
the star collapses as there isn't enough energy for fusion the star gets compressed by gravity and particles this compression suddenly reverses causing an explosion
35
what are the two things a supernova can result in
a black hole | a neutron star
36
how is a neutron star formed
the neutron star is the very dense core of the supernova
37
what is a black hole
a super dense point in space that not even light can escape from
38
how are lighter elements formed
from nuclear fusion in the sun and stars
39
why can elements larger than iron not be formed by fusion
too much energy is needed
40
how old is the sun
5 billion years
41
what will happen in 5 billion years
the sun will turn into a red giant then a white dwark then a black dwarf as it stops emitting energy
42
how are elements heavier than iron formed
a supernova explosion
43
why has all the uranium, on earth not decayed by now
very long half life
44
how are new stars and planets formed by a supernova
forces such as gravity pull all the debris together and ensures it has every element
45
what is produced when a supernova explodes
every known element
46
how are elements heavier than iron produced and distributed
the force of a red supergiant collapsing is great enough to force two smaller nuclei to fuse into a bigger one and the explosion of a supernova distributes them all over the unviverse
47
what is the orbit of the earth like
almost circular
48
what is the force on an orbiting object
the gravitational attraction between it and the larger body
49
what is a galaxy
a huge collection of stars that star together because of gravity
50
how long does it take to travel one light year
one year
51
which colour had the longest wavelength
red
52
what increases as the speed of a star or galaxy increases
the red shift
53
what did Edward Hubble discover 2
the light form distant galaxies was red shifted the further away a galaxy is from earth the great the wavelength
54
what happens to the light rays of something that is moving from you
the wavelength increases
55
why is it called the red shift
as something moves away from you the wavelength increases | it is shifted to the red end of the spectrum as this is where the longest waves are
56
what happens to the light rays of something if it is moving towards you
they get squashed together and shifts to the blue end of the spectrum where they are most squashed
57
what is it called when something moves towards you
blue shift
58
what is happening to the universe
it is expanding
59
the big bad theory of expansion
everything started in a very small and dense area | the big band explosion started things off to expand the unviverse
60
what is the steady state theory of expansion
the galaxies are being pushed apart by matter entering through white holes
61
evidence for the big band theory
scientists have discovered microwaves coming form every direction in space that can only have come form the radiation released during the big bang
62
what is CMBR
Cosmic microwave background radiation | gamma radiation produced just after a Big Bang
63
what is dark matter
the missing mass in galaxies can be seen
64
what will happen if the density of the universe is less than a specific amount
it will continue expanding forever and everything will die out
65
what will happen if the density of the universe is above a specific amount
it will stop expanding and go into reverse th big crunch
66
what are the two possibilities for the end of the universe
the big Yawn | the big crunch
67
what energy is thought to be causing the expansion
dark energy
68
what are geostationary orbits
the object orbits the same earths in the same direction as the earths spin so it stays above the same place
69
when you get close to a star or planet what increases
the gravitational attraction force
70
as the gravitational force increases what much happen to the object orbiting the larger body
its speed must increase
71
why must the speed of an orbiting object increase as the gravitational attraction increases
it must speed up to overcome the force of attraction and avoid crashing with the bigger body and to sty in orbit
72
what happens to the speed of an orbiting object the further from the larger body it is and why
it slows down the force of gravity on the object is less sp doesn't need to travel as fast to stay in orbit
73
what happens to the size of the orbit the further away a satellite is from earth
it increases and takes longer to complete one orbit
74
what direction does the force of gravers form the sun air
it acts form the centre of the sun to the planet pulling towards it
75
if the speed of an object in a stable orbit increases what happens to the radius of its orbit
it will decrease
76
what is a centripetal force
a force acting towards the centre pf a circle
77
what is the velocity of a planet
its direction of motion
78
what to remember about the force of gravity on a planet and its direction of motion
they are at right angles to eachother
79
why does an orbiting planet always accelerate
it is constantly changing direction gravity changes its velocity to pull the planet towards the sun but because the planet is already moving it just changes its direction rather than making it fall towards the sun
80
what is the accelerating of a planet
the change per second in its velocity
81
what happens if a satellite is released too close to earths surface
atmospheric drag means it gradually loses speed and crashes into earths surface
82
what happens if a satellite is released quickly from earth
it will Fly off into space
83
what happens when a satellite is released correctly
it moves at a constant height and speed in a circular stable orbit around the earth
84
what happens when the speed of a rocket increases to keep it constant
the increase in speed moves it to a higher orbit where the increased distances means its slower keeping it constant

PHYSICS (16 decks)

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