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GCSE Physics > Topic 7 - Astronomy > Flashcards

Topic 7 - Astronomy Flashcards

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1
Q

SP7a - What is the geocentric model?

A

The model of our solar system in which everything orbits the earth.

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2
Q

SP7a - What is the heliocentric model?

A

The current model of our solar system where the sun is at the centre and other planes orbit it.

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3
Q

SP7a - What shape is the earth’s orbit around the sun?

A

Elliptical

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4
Q

SP7a - What developments in techonology have allowed us to make more detailed observations?

A
  • Computers allow detailed analysis.
  • Photography allows accurate and permanent storage of events.
  • Telescopes can now be place outside of the earth’s atmosphere giving wider and more detailed detection.
  • Space probes allow better analysis of the solar system.
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5
Q

SP7a - Why are telescopes place outside the earth’s atmosphere more detailed than a regular telescope?

A
  • The earth’s atmosphere absorbs many waves of the EM spectrum.
  • Outside the atmosphere, these could be detected. (such as infrared radiation)
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6
Q

SP7b - What is the difference between weight and mass?

A

Your weight is the force acting on you dependant on your mass and the gravitational field strength.

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7
Q

SP7b - What is the gravitational field strength on earth?

A

9.81 N/Kg

(Can be rounded to 10N/Kg)

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8
Q

SP7b - What are the four types of orbits for artificial satellites?

A
  • Highly elliptical
  • Circular geostationary
  • Low earth orbits
  • Polar orbits
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9
Q

SP7b - What is a geostationary orbit and what are these satellites used for?

A
  • Satellites that stay in the same place relative to the earth’s position.
  • They move at 3070 m/s and are used for broadcasting.
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10
Q

SP7b - A satellite in which type of orbit will eventually pass over all parts of the earth?

A

Polar orbits

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11
Q

SP7b - A satellite in which type of orbit needs the least fuel for launching?

A

Low earth orbits

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12
Q

SP7b - A satellite in which type of orbit is used for communication with parts of the earth near the poles?

A

Highly elliptical orbits

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13
Q

SP7b - Why doesn’t a satellite continue moving in a straight line?

A

The gravitational force between the earth and the satellite causes it to continuously change direction and orbit the earth.

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14
Q

SP7b - At what angle is the force between the earth and satellite?

A

90°

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15
Q

SP7b - Explain the speeds that a satellite would have to be travelling at in relation to its orbit, and the changes in orbit it would experience if it changed speed.

A
  • The gravitational force on an object in a lower orbit is a stronger than at a higher orbit so a satellite at a lower orbit would have to travel at a higher speed to stay in orbit.
  • Once it eventually slows down, it will drop towards earth.
  • However as it drops it gains speed and will eventually be able to be at a lower orbit at a faster speed.
  • Once it drops enough that it passes through the earth’s atmosphere, the air resistance will slow it down and it will eventually fall to earth.
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16
Q

SP7b - What reaction takes place inside a star?

A

Nuclear fusion

(typically H + H = He)

17
Q

SP7b - Describe the life cycle of a star the size of our sun. [6 Marks]

A
  • It starts with a Nebula (A cloud of gas).
  • The particles in this pull themselves together, becoming denser until their own gravity causes it to collapse in on itself forming a protostar.
  • Eventually the pressure and temperature in the protostar become large enough that nuclear fusion starts to occur converting hydrogen to helium
  • The energy released form the fusion reactions push the star outward causing it to expand.
  • Once the force of the gravity pulling the star inwards matches the force of pressure from the fusion reactions, the star will be at a steady size and in its main sequence stage where it continues to convert hydrogen to helium
  • Eventually, hydrogen runs out and heavier reactions take place.
  • This creates more energy which expands the star more
  • The outermost layers are no longer held in place by the force of gravity so they expand forming a red giant
  • Once all the fuel has run out, all the layers disband forming a shell of gas.
  • This leaves behind a highly dense white dwarf which doesn’t carry out any reactions.
18
Q

SP7b - Describe the life cycle of a star much larger than our sun. [6 Marks]

A
  • It starts with a Nebula (A cloud of gas).
  • The particles in this pull themselves together, becoming denser until their own gravity causes it to collapse in on itself forming a protostar.
  • Eventually the pressure and temperature in the protostar become large enough that nuclear fusion starts to occur converting hydrogen to helium
  • The energy released form the fusion reactions push the star outward causing it to expand.
  • Once the force of the gravity pulling the star inwards matches the force of pressure from the fusion reactions, the star will be at a steady size and in its main sequence stage where it continues to convert hydrogen to helium
  • Eventually, hydrogen runs out and heavier reactions take place.
  • This creates more energy which expands the star more forming a red supergiant.
  • These heavier fusions are carried out all the way to iron when it runs out of fuel.
  • The star rapidly collapses causing a supernova
  • This leaves behind a very dense neutron star
  • If the mass of the star is even larger, then a black hole is formed in place of the neutron star.
19
Q

SP7d - What is the doppler effect?

A

When the pitch of a noise get lower as it travels aways from you. (and higher when it travels towards you)

20
Q

SP7d - Why does the doppler effect occur?

A

As a sound travels, the wavelengths are squashed or stretched meaning the sound’s pitch appears higher or lower.

21
Q

SP7d - What is red-shift?

A

When light form distant galaxies shift towards the red side of the spectrum due to wavelengths being stretched as the galaxy moves away from earth.

22
Q

SP7d - What do we use to check red-shift?

A

Absorption spectrums of the galaxy compared to the absorption spectrum of the sun.

23
Q

SP7e - What are the two main theories for the origin of the universe?

A
  • The big bang theory
  • Steady state theory
24
Q

SP7e - What is the Big Bang Theory?

A
  • The whole universe started out from one point of concentrated energy.
  • All matter started form this point and continued to expand outwards as the universe constantyl expands.
25
Q

SP7e - What is the Steady State Theory?

A

The universe always existed and as it expands matter is continuosly created.

26
Q

SP7e - Which theory of the universe is the currently accepted theory?

A

The Big Bang Theory

27
Q

SP7e - What provides evidence for both theories of the universe and why?

A

Red-shift; as galaxies are constantly moving away the universe is constantly expanding.

28
Q

SP7e - What provides evidence for the currently accepted theory.

A

CMBR (Cosmic Microwave Background Radiation) is found throughout all of the universe at the same rate suggesting that it all started form one point and expanded out from there.

29
Q

SP7e - What can we use as a model of why CMBR proves The Big Bang Theory?

A
  • A Currant bun has currants close together.
  • As the dough rises, the number of currants stay the same but they are found at consistent rate throughout the bun.
30
Q

SP7d - What does it mean if one galaxy has a greater red-shift than another?

A

That galaxy is further away and moving faster than the other.

GCSE Physics (17 decks)

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