1
Q
what is a universe
A
large collection of billions of galaxies
2
Q
galaxy
A
a large collection of billions of stars
3
Q
our solar system is in what galaxy
A
the milky way
4
Q
what is at the centre of our solar system
A
the sun
5
Q
gravitational field strength varies how
A
strength of gravity in different planets affects an objects weight on that planet
6
Q
weight
A
force acting on an object due to gravitational attraction
7
Q
fore of weight is responsible for (3)
A
- objects staying firmly on the ground
- objects always falling to the ground
- satellites being kept in orbit
8
Q
gravitational field strength depends on (2)
A
mass (greater the mass, greater the g)
distance from its centre (closer you are the stronger it is)
9
Q
g on earth
A
10 N/Kg
10
Q
higher gravitational field strength means
A
a larger force of attraction towards the centre of the planet or moon
11
Q
does the mass of an object vary
A
no
12
Q
does the weight of an object vary
A
yes depending on what planet its on, gravitational field strength
13
Q
why does gravitational field strength vary (2)
A
as you move further away from a planet, gravity decreases
bigger mass= stronger gravity
14
Q
smaller/larger bodies orbit smaller/larger bodies
A
smaller
larger
15
Q
planets orbit the
A
sun
16
Q
moons orbit the
A
planets
17
Q
comets orbit the
A
sun
18
Q
artificial satellites orbit the
A
earth
18
Q
orbital motion is a result of
A
the gravitational force of attraction acting between 2 bodies.
19
Q
asteroids orbit the
A
sun
20
Q
gravitational force always acts in what direction
A
towards the centre of the larger body, causing smaller body to move in a circular motion
21
Q
similarities in the way different planets orbit the sun (3)
A
- all orbit on the same plane
- all travel in the same direction
- orbits are all slightly eliptical
22
Q
differences in the way different planets orbit the sun (3)
A
- orbit at different distances from the sun
- orbit at different speeds
- all take different amounts of time to orbit the sun
23
Q
planets closest to sun take how long and why
A
shortest amount of time as they are the fastest
24
planets furthest from the sun take how long to orbit sun and why
longest amount of time as they travel at slowest speeds
25
orbital motion of moons (3)
- orbit in circular path
- some planets have more than one moon
- the closer the moon to the planet, the shorter the time taken to complete and orbit and the greater the speed
26
orbital motion of comets (3)
highly eliptical
as comet approaches sun, speed increases
as it moves further away from the sun, its speed decreases
27
the comets orbital motion are highly eliptical, so?
speed changes significantly as their distance from the sun changes
28
do all comets orbit in the same plane
no, some don't even go in the same directions
29
what causes artificial satellites to orbit the earth
the gravity of the earth keeps them in orbit,
and they're launched at high speeds and gravity bends their path into a continuous curved orbit around the earth
30
what is an orbital period
time taken for an object to perform one orbit
31
extremely hot objects emit what radiation
what does this mean
visible light and infrared which means that the colour they emit depends on how hot they are
32
red star is
coolest
33
blue star is
hottest
34
colour of a star is related to its
surface temperature
35
as astronomical objects cool, they
expand
36
as astronomical objects heat, they
contract
37
when a star becomes a red giant, it does what
expands, cools and becomes redder
38
when a star becomes a white dwarf, it
contracts, heats up and gets whiter
39
life cycle of solar mass stars
stellar nebula → protostar → main sequence star - THEN EITHER STARS WITH MASS LOWER THAN SUN, OR STARS WITH MASS LARGER THAN SUN
40
nebula
a large interstellar cloud of dust and gas
41
how does a protostar form
The force of gravity within a nebula pulls the particles closer together until a hot ball of gas forms, known as a protostar
As the particles are pulled closer together the density of the protostar will increase
This results in more frequent collisions between the particles which causes the temperature to increase
42
how does a main sequence star form
Once the protostar becomes hot enough, nuclear fusion reactions occur within its core
Once a star initiates fusion, it is known as a main-sequence star
During the main sequence, the star is in equilibrium and said to be stable
43
low mass star cycle
red giant → planetary nebula → white dwarf
44
red giant forms how
After several billion years, the hydrogen causing the fusion reactions in the star will begin to run out
Once this happens, the fusion reactions in the core will start to die down
The star will begin to fuse helium which causes the outer part of the star to expand
As the star expands, its surface cools and it becomes a red giant
45
white dwarf forms how
Once the helium fusion reactions have finished, the star collapses and becomes a white dwarf
The white dwarf cools down over time and as a result, the amount of energy it emits decreases
46
larger mass cycle
red supergiant → supernova → neutron star / black hole
47
key differences between lower mass and larger mass stars
A higher mass star will stay on the main sequence for a shorter time before it becomes a red supergiant
A lower mass star fuses helium into heavy elements, such as carbon, whereas a higher mass star fuses helium into even heavier elements, such as iron
48
red supergiant forms how
After several million years, the hydrogen causing the fusion reactions in the star will begin to run out
Once this happens, the fusion reactions in the core will start to die down
The star will begin to fuse helium which causes the outer part of the star to expand
As the star expands, its surface cools and it becomes a red supergiant
49
supernova forms how
Once the fusion reactions inside the red supergiant cannot continue, the core of the star will collapse suddenly and cause a gigantic explosion called a supernova
At the centre of this explosion, a dense body called a neutron star will form
The outer remnants of the star are ejected into space forming new clouds of dust and gas (nebula)
The heaviest elements are formed during a supernova, and these are ejected into space
These nebulae may form new planetary systems
50
neutron star is formed how
forms when a massive star explodes in a supernova and its core collapses, compressing into an extremely dense ball of neutrons.
51
what happens to neutron stars
in the case of the most massive stars, the neutron star that forms at the centre will continue to collapse under the force of gravity until it forms a black hole
A black hole is an extremely dense point in space that not even light can escape from
52
what is the luminosity of a star
the total amount of light energy emitted by the star
53
brightness of a star depends on (2)
- luminosity of a star
- distance star is from earth
54
apparent magnitude is
the percieved brightness of a star as seen from earth
55
the brighter the star, the __ the magnitude
lower
56
the dimmer the star, the __ the magntidue
higher
57
what is absolute magnitude
a measure of how bright stars would be if they were all placed the same distance away from earth
58
on a HR diagram, surface temperature is plotted on what axis, and from what to what
X-axis
hottest to coolest
59
on a HR diagram brightest stars will be
near the top
60
on a HR diagram, dimmest stars will be
near the bottom
61
on a HR diagram, hottest stars will be
on left
62
on a HR diagram, coolest stars will be
on right
63
what is shown on the y-axis of a HR diagram
luminosity
64
surface temperature on a HR diagram is measured in
Kelvin
65
most stars are found on the
main sequence
66
on a HR diagram, below main sequence to the left are
white dwarfs
67
on a HR diagram above the main sequence on the right are
red giants
68
on a HR diagram, above the red giants are
red super giants
69
what is the big bang theory
around 14 billion years ago, the universe began from a very small region that was extremely hot and dense
there was a giant explosion known as the big bang
this caused the universe to expand from a single point
each point expands away from each other
as a result of this, the universe continues to expand
70
evidence for big bang (2)
galactic red shift
cosmic microwave backround radiation
71
how is galactic red shift evidence for the big bang
it shows galaxies are moving further away from us as the ones further away are seen more red (redshift) which happens due to the doppler effect.
Observations show that the further away a galaxy is, the more its light is red-shifted.
This suggests the universe is expanding in all directions, which is exactly what we’d expect if it started from a single point — the Big Bang.
72
what does red shift mean
the light from distant galaxies is stretched to longer (redder) wavelengths.
73
galaxies further away have a ___ speed
faster
74
evidence from CMB radiation
it matches what the theory predicted. The Big Bang said the universe started very hot, so some heat should still be left over. As the universe grew, that heat cooled down and became microwave radiation that we see everywhere in space today. The CMB is almost the same in every direction, which shows the universe was once smooth and very hot. Its temperature is very cold now—about 2.7 K—which fits with the idea that the universe has been cooling as it gets bigger.
75
what is redshift
phenomenon of the wavelength of light appearing to increase when the source moves away from an observer
76
if an object moves towards an observer, wavelength of light
decreases
77
Describe the red-shift in light received from galaxies at different distances away from the Earth:
The light from galaxies far away from Earth is shifted toward the red end of the spectrum, meaning its wavelength is longer than expected. The farther away a galaxy is, the greater this red-shift becomes. This means distant galaxies have their light stretched more than closer ones.
78
Explain why the red-shift of galaxies provides evidence for the expansion of the universe
The red-shift shows that galaxies are moving away from us. Since all galaxies are moving away and the farther ones move faster (more red-shift), it means the space between galaxies is stretching. This is strong evidence that the universe is expanding, as predicted by the Big Bang theory.
PHYSICS IGCSE
flashcards
Decks in class (32)
# Cards
-
Energy and pressure32
-
energy resources64
-
energy18
-
density8
-
pressure ( gas pressure)15
-
changes of state and internal energy stores22
-
specific heat capacity9
-
magnetic field lines17
-
induced magnets and magnetism7
-
electromagnetism10
-
electromagnets and solenoids14
-
force on a current carrying conductor4
-
fission and fusion and nuclear reactors49
-
Waves ( properties of waves )57
-
Waves ( The electromagnetic spectrum)49
-
Waves ( light and sound)54
-
radioactivity93
-
Magnetism42
-
electromagnetism10
-
momentum21
-
moments11
-
Hookes law13
-
forces, movement & changing shape33
-
Stellar evolution41
-
astrophysics79
-
electromagnetism16
-
stopping distance7
-
terminal velocity4
-
electricity9
-
static electricity and electric charge17
-
electromagnetic induction9
-
circuits16
