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AQA Physics PHYA5 - Thursday 18th June 2015 [Exam Discussion Thread] Watch

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    (Original post by CD223)
    I see. I need to revise it too. I'd struggle to answer a six marker on that even though it's probably one of the "easier" topics. I can give an order but not reasons (EG: hydrogen runs out and star swells etc)


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    totally agree that stars will came up on the astro paper, any predictions for section A i think it will be thermal for the 6 marker as its only come up on the june 2011 paper...
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    (Original post by Hellomoto.)
    totally agree that stars will came up on the astro paper, any predictions for section A i think it will be thermal for the 6 marker as its only come up on the june 2011 paper...
    Personally, I can see a SHC experiment.


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    (Original post by CD223)
    I see. I need to revise it too. I'd struggle to answer a six marker on that even though it's probably one of the "easier" topics. I can give an order but not reasons (EG: hydrogen runs out and star swells etc)


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    Maybe it would be good practice if any of us who want to write out an answer to a theoretical six marker, like you suggested (e.g. X has a larger mass (>3 solar masses) and Y has a lower mass (~1.4 solar masses), describe the life cycle of these stars), and then compare points between us to see what would likely be necessary to get the marks?
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    (Original post by Lau14)
    Maybe it would be good practice if any of us who want to write out an answer to a theoretical six marker, like you suggested (e.g. X has a larger mass (>3 solar masses) and Y has a lower mass (~1.4 solar masses), describe the life cycle of these stars), and then compare points between us to see what would likely be necessary to get the marks?
    I'd be up for that? I'll try and write an answer. It won't be great, mind, haha.


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    (Original post by CD223)
    I'd be up for that? I'll try and write an answer. It won't be great, mind, haha.


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    I haven't done any revision lately for physics (don't even have any notes with me tonight oops) so I don't expect mine will be great either! But anything is a good starting point and if it actually does come up in the exam we'll be prepared
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    (Original post by Lau14)
    I haven't done any revision lately for physics (don't even have any notes with me tonight oops) so I don't expect mine will be great either! But anything is a good starting point and if it actually does come up in the exam we'll be prepared
    I'll get 'star'ted (pun was necessary) tonight.


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    (Original post by CD223)
    I'll get 'star'ted (pun was necessary) tonight.


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    Puns are always necessary I'll probably do mine shortly
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    X has a larger mass (>3 solar masses) and Y has a lower mass (~1.4 solar masses), describe the life cycle of these stars.
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    Both star X and Y begin when dust and gas in a nebula slowly coalesce under gravity to form a protostar. As gravity pulls the gas in, it heats up, and eventually reaches ignition temperature and fusion of hydrogen into helium begins. When hydrostatic pressure outwards from fusion equals the force of gravity pulling inwards then the star is stable (a main sequence star).
    Hydrogen fusion takes place at the core of the star. When hydrogen in this region has all been fused into helium, fusion slows, therefore decreasing outwards pressure. The outer layers are pulled inwards and Helium and heavier elements undergo fusion (nuclei up to iron, the most stable, are formed). Hydrogen fusion continues outside the core, forming more Helium and causing the star to rapidly increase in size to a red giant (Y) or a red supergiant (X).

    When star Y runs out of fuel for fusion, the outer layers separate from the core and form a planetary nebula. The remaining core is a white dwarf, which eventually cools to a black dwarf.

    Star X has a large enough mass that when fusion stops, gravity pulls it in on itself. A star with a core of around 1.5-3 solar masses will form a neutron star - the star has enough mass to overcome electron degeneracy, and electrons are forced into protons to form neutrons. The star has a density equal to the density of a nucleus. The outer layers fall onto this core and rebound in a supernova. Elements heavier than iron are produced.
    If star X has a mass larger than this, it will form a black hole (an object with an escape velocity faster than the speed of light).
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    Anyone have any tips for tackling the special relativity question calculations. They're not always 100% clear and it can be quite frustrating


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    (Original post by CD223)
    Anyone doing astro?

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    im doing astro although feeling a tad lost with it all. its just not sinking in and a lack of notes isn't helping
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    (Original post by Lau14)
    X has a larger mass (>3 solar masses) and Y has a lower mass (~1.4 solar masses), describe the life cycle of these stars.
    Spoiler:
    Show
    Both star X and Y begin when dust and gas in a nebula slowly coalesce under gravity to form a protostar. As gravity pulls the gas in, it heats up, and eventually reaches ignition temperature and fusion of hydrogen into helium begins. When hydrostatic pressure outwards from fusion equals the force of gravity pulling inwards then the star is stable (a main sequence star).
    Hydrogen fusion takes place at the core of the star. When hydrogen in this region has all been fused into helium, fusion slows, therefore decreasing outwards pressure. The outer layers are pulled inwards and Helium and heavier elements undergo fusion (nuclei up to iron, the most stable, are formed). Hydrogen fusion continues outside the core, forming more Helium and causing the star to rapidly increase in size to a red giant (Y) or a red supergiant (X).

    When star Y runs out of fuel for fusion, the outer layers separate from the core and form a planetary nebula. The remaining core is a white dwarf, which eventually cools to a black dwarf.

    Star X has a large enough mass that when fusion stops, gravity pulls it in on itself. A star with a core of around 1.5-3 solar masses will form a neutron star - the star has enough mass to overcome electron degeneracy, and electrons are forced into protons to form neutrons. The star has a density equal to the density of a nucleus. The outer layers fall onto this core and rebound in a supernova. Elements heavier than iron are produced.
    If star X has a mass larger than this, it will form a black hole (an object with an escape velocity faster than the speed of light).
    This is great! I'll make sure I look over and try and add to this tonight

    Thank you


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    (Original post by Fireiscatching1)
    im doing astro although feeling a tad lost with it all. its just not sinking in and a lack of notes isn't helping
    Have you seen the AQA Nelson Thornes course notes? They're pretty useful.


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    Burdittphysics on YouTube gives nice examples for the multiple choice section
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    (Original post by Amanzz)
    Anyone have any tips for tackling the special relativity question calculations. They're not always 100% clear and it can be quite frustrating


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    I still haven't done questions on that topic. In fact i haven't finished that topic yet
    What's absurd about the questions?


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    (Original post by CD223)
    This is great! I'll make sure I look over and try and add to this tonight

    Thank you


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    Needs some work doing on it (eg actually comparing it with my notes etc!) but not too bad considering we've got a while until the exam!
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    (Original post by Lau14)
    Needs some work doing on it (eg actually comparing it with my notes etc!) but not too bad considering we've got a while until the exam!
    I'm trying not to rely too heavily on the week between exams :L


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    Name:  Screen Shot 2015-05-24 at 21.21.44.png
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    In a question such as this, I would be tempted to give the answer:

    "Rain, pollution, cloud coverage"

    Could the mark be penalised?
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    (Original post by JaySP)
    Name:  Screen Shot 2015-05-24 at 21.21.44.png
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    In a question such as this, I would be tempted to give the answer:

    "Rain, pollution, cloud coverage"

    Could the mark be penalised?
    It's hard to say. What is the actual answer?

    You are correct, it just depends on how specific they want you to be.

    Personally, I would say "water (vapour)".


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    (Original post by CD223)
    It's hard to say. What is the actual answer?

    You are correct, it just depends on how specific they want you to be.

    Personally, I would say "water (vapour)".



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    Water vapour is the correct answer buts lets say i did put that instead of rain. Would i have still got the mark amidst the other answers?
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    (Original post by JaySP)
    Water vapour is the correct answer buts lets say i did put that instead of rain. Would i have still got the mark amidst the other answers?
    Does that mark scheme allow for other answers? It depends on what the MS actually says. "Any sensible answer" is sometimes included.

    That said, because it said "in the atmosphere", it makes me think of a particular element/compound in the atmosphere, over physical entities such as clouds.


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