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GCSE- Physics > Topic 7- Astronomy > Flashcards

Topic 7- Astronomy Flashcards

1
Q

Why does the weight of objects change on different planets? e.g the Earth and the moon

A
  • As F =G(mass1 x mass2)/Distance ^2
    • G is a constant 6.674
  • Meaning an object with LESS MASS (the moon) will have a SMALLER GRAVITATIONAL force (than the earth)
  • As Weight= Gravitational field strength x mass
  • An object on the moon (with the same mass) will weigh less
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2
Q

What is the gravitational field strength of the moon?

A
  • 1.6 N
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3
Q

What is the gravitational field strength of the Earth?

A
  • 9.8 N
  • 10N
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4
Q

What is the (our) solar system made of?

A
  • The sun
  • Eight planets
    -Dwarf planets
  • Natural sateleits (moons, asteroid, comets)
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5
Q

What are the names of the planets in order?

A
  • Mercury
  • Venus
  • Earth
  • Mars
  • Jupiter
  • Saturn
  • Uranus
  • Neptune
  • (Pluto, dwarf)
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6
Q

How have ideas surrounding the solar system changed over time?

A

Geocentric- idea that the Earth was the centre of the solar system, and the sun, moon and planets orbited

Heliocentric- Idea that the sun is at the centre of the solar system, that the planets orbit it, and moons orbit the planets

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7
Q

What did the geocentric model not prove?

A
  • Why planets changed brightness ( because they are not always the same distance from Earth)
  • Jupiter and mars appeared to move backwards sometimes
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8
Q

What in our solar system have a circular orbit/ slightly elliptical?

A
  • Moon
  • Planets
  • Asteroid
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9
Q

What in our solar system have a highly elliptical orbit?

A
  • Comets
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10
Q

Low Earth orbits: Height, speed, time to orbit, use

A
  • 160 Km -> 2000km above Earth’s surface
  • 7780 m/s
  • 1.5/2 hours to orbit
  • ISS (international space station)
  • Communications
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11
Q

Polar Orbit: Height, speed, time to orbit, use

A
  • About 160- 2000km above Earth’s surface
  • 7500 m/s
  • 1.5 hours
  • Goes over poles
  • Monitors weather, used for spying/image taking
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12
Q

Geo-stationary: Height, speed, time to orbit, use

A
  • 35,900 km above Earth’s surface
  • 3000 metres/s
  • 24 hours
  • Communications, television, weather
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13
Q

Elliptical: Height, speed, time to orbit, use

A
  • Faster closer to the Earth
  • Communications
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14
Q

How does a circular orbit due to gravity mean change in velocity but not speed?

A
  • Gravity acts as the CENTRIPETAL force keeping the object in a circular orbit (changes linear direction)
  • Velocity is a VECTOR quantity and changes as DIRECTION CHANGES
  • Speed is a scalar quantity
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15
Q

What is the equation for the (centripetal) force in a circular motion?

A

F= mv^2/ radius

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16
Q

Explain how, for a stable orbit, the radius must change if
orbital speed changes (qualitative only)

A
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17
Q

What happens when the radius changes in a stable orbit (same centripetal force)?

A
  • As f=mv^2/r
  • If the velocity changes, but the mass and force remain constant
  • Radius must change to keep the constant
  • If speed increases, radius must increase
  • If speed decreases, radius must decrease.
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18
Q

What happens when the speed of a satellite decreases?

A
  • Falls out of orbit, towards the centre (Earth) by gravity
  • Gains speed when accelerating towards the Earth
  • Stabilises as speed begins to increases and radius decrease for the F and M to be constant (F=mv^2/r)
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19
Q

Do objects in a lower orbit feel more gravity?

A
  • Yes
  • Lower radius means the object feels more gravity and therefore has to move faster
20
Q

What happens if a satellite is moving too fast?

A
  • Force of gravity cannot keep it in circular motion as it is too fast
  • Moves off into space
  • 11,200 metres/sec
21
Q

Why are v and r always inversely proportional?

A
  • Force felt= g(m1xm2)/r^2
  • Force= mv^2/r
    simplified
    v^2= g(m1, the larger body’s mass)/ r
    Therefore if v is to increase, r has to decrease as gravity (6.67) and mass are constant
22
Q

What in the equation F=mv^2/r changes when radius increases?

A
  • V and R are inversely proportional ( v^2= g(6.67) x m1/ radius
  • When R increases Velocity has to decrease
  • meaning force felt is NOT CONSTANT
  • F also DECREASES.
23
Q

Steady state: How the world began, Expansion, Density

A
  • Always existed
  • New matter is created by expansion
  • Density remains the same as new matter (mass) is being created at the same rate of expansion (volume)
24
Q

Big bang: How the world began, Expansion, Density

A
  • All universe (abt 14 billion years ago) was a very small and dense region which exploded
  • Explosion caused rapid continuous
    expansion
  • Density decreases as no new matter (m) is created but the universe (v) is expanding
25
Q

What is red shift?

A
  • Spectrum of colours absorbed by (our atmosphere) are more red shifted on the spectrum
  • As light travels to us, space expands and thus the light’s wavelength increases
  • Causes more red shifted light to travel to us (thus more red shifted light is absorbed)
26
Q

What is CMB radiation?

A
  • Cosmic microwave background radiation
  • Earliest form of light emmitted
  • Radiation emitted from all directions
  • As space expands the wavelength of CMB increased into microwaves
27
Q

How does red shift prove both steady state and big band?

A
  • Both believe universe is expanding
  • Steady state believes universe is expanding and new mater is being created between already existing places
28
Q

What does cmb prove?

A
  • The big band theory
  • That all matter came from one place
29
Q

What happens to an observer when the object emitting light/ sound is heading towards us?

A
  • Higher frequency/ lower wavelength
  • Purple/ blue
  • Higher pitch
30
Q

What happens to an observer when the object emitting light/ sound is heading towards us?

A
  • Larger distance between waves
  • Higher wavelength, lower frequency
  • Red shifted colour
  • Lower pitch
31
Q

Why the further away a galaxy the more red shifted it is?

A
  • More distance between two objects
  • More space expands
  • More red shifted/ longer wavelength
32
Q

How was CMB discovered?

A
  • Accidentally by two Americans on a radio
  • Noticed a noise constant from every direction
33
Q

What is the starting sequence of every star?

A

Nebula
Protostar
Main sequence star

34
Q

What comes after a main sequence star of smaller mass?

A
  • Red giant
  • White dwarf
  • Black dwarf
35
Q

What comes after a main sequence star of larger mass?

A
  • Red super-giant
  • Supernova
  • Neutron star or Blackhole
36
Q

What is and how does a nebula become a protostar?

A

Nebula- cloud of gas and dust

gravity draws the cloud together causing rise in density and temperature and pressure

Protostar- Nuclear fusion begins where hydrogen is turned into helium generating energy

37
Q

How does pressure change a protostar into a main sequence star?

A
  • As pressure increases due to nuclear fusion
  • thermal expansion occurs- pressure from hot gas
  • Causes expansion as FORCE due to pressure is stronger than gravity
  • Pressure then decreases and gravity causes the star to shrink slightly
  • Constant imbalance but stable
38
Q

How long is a star a main sequence star?

A

-For most of its life
- Our sun for 10 billion years

39
Q

Why do stars become red giants/ supergiants?

A
  • Core runs out of hydrogen
  • Uses helium as its fuel to form carbon
40
Q

What is a white dwarf and what does it become?

A
  • Very small dense core
  • Initially very hot but cools into
  • A black dwarf (cold)
40
Q

What happens to red giants?

A
  • Unstable
  • expels outer layers quickly
  • Turns into a white dwarf
41
Q

What happens to a red supergiant?

A
  • After a few million years all helium is used up
  • Starts to use carbon as its fuel
  • Continuous until it builds up an iron core
  • Explodes as the core succumbs to gravity and there is no fuel left (supernova)
42
Q

What happens during a supernova and after?

A
  • All elements heavier then iron are crated and expelled into space
  • smaller mass core becomes a neutron star
  • Larger mass core collapses into a black hole
43
Q

What did the invention of photography allow for astronomers?

A

Ability to take photos of the universe that we are unable to see

44
Q

Why are telescopes placed outside the Earth’s atmosphere?

A
  • Atmosphere absorbs radiation the telescopes needed to detect
  • Away from the blurring effect of the atmosphere- clearer images
45
Q

What did the invention of computers allow astronomers to do?

A

1960S create the first detailed model of supernova explosions

46
Q

What did the invention of telescopes allow us to see?

A

Earth’s place in the heliocentric solar system
- Planets and asteroids
- Mountains and craters on the moon

GCSE- Physics (8 decks)

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