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    (Original post by lefneosan)
    Hi does anyone know if there is any interaction between white dwarfs and red giants? e.g. main sequence become red giants which then become white dwarfs?
    What you said is correct. Red giant dead = white dwarf. [which then, should, theoretically, become a black dwarf].

    (Original post by Sasukekun)
    I am so sweating it about this exam. I've read all three of my text books, done those 200 past paper question someone linked, made brief notes, revised over and researched things I didn't quite fully understand and now reading through the syllabus making sure I know everything and making experiment plans that they might ask us. All in all I know it could be worthless if Edexcel bring some (and they will since it's a requirement) annoying applied physics bit that I won't understand ._. I think I've done the most I can though (props to the 11 day period between this exam and the previous one).
    You'll do fine!
    I've not bothered reading half of my textbooks (I have 5, I think), only done a selection of the 200 questions, researched bits and pieces..and therefore, if anyone's failing, it's me!

    Out of interest, what was your last exam? 11 days is just not fair! :p:
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    (Original post by unamed)
    What you said is correct. Red giant dead = white dwarf. [which then, should, theoretically, become a black dwarf].



    You'll do fine!
    I've not bothered reading half of my textbooks (I have 5, I think), only done a selection of the 200 questions, researched bits and pieces..and therefore, if anyone's failing, it's me!

    Out of interest, what was your last exam? 11 days is just not fair! :p:
    XD You'll do fine. And cheers. Last exam was C4, when/what was yours?
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    (Original post by Sasukekun)
    XD You'll do fine. And cheers. Last exam was C4, when/what was yours?
    I hope so, I have my pride at stake, if nothing else! XD
    Luck you.
    Economics, Friday. Exciting, it was. I got so bored half-way through, I ended up staring at the ceiling for some time before I realised I had only an hour left for the rest of the paper! :p: [it's a long paper]
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    =[
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    ughh stupid stupid stupid oscillations
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    could someone explain the displacement-time graph for an overdamped object? I dont get why the displacement does not go all the way to zero
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    to dimi3
    The displacement follows a exponential decay pattern.
    Since e^-x never touches the x-axis, displacement should also never become zero theoretically. But in real life situation, it does become zero after a while.
    oops, my bad. I see you said critical damping.
    In critical damping, the displacement does become zero.
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    sorry about all the posts but help me please :woo:
    so this is how i understand resonance, tell me if i got anything wrong
    If the driving frequency of an object matches its natural frequency, it will absorb more energy (this is because were supplying it with energy right?), increasing its amplitude. A situation like this is called resonance. (so would that mean in resonance the amplitude is always increasing?)
    yeah?:unsure:
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    (Original post by ananda2010)
    to dimi3
    The displacement follows a exponential decay pattern.
    Since e^-x never touches the x-axis, displacement should also never become zero theoretically. But in real life situation, it does become zero after a while.
    oops, my bad. I see you said critical damping.
    In critical damping, the displacement does become zero.
    lol i did say critical damping but i meant overdamping :mmm:
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    (Original post by dimi3)
    sorry about all the posts but help me please :woo:
    so this is how i understand resonance, tell me if i got anything wrong
    If the driving frequency of an object matches its natural frequency, it will absorb more energy (this is because were supplying it with energy right?), increasing its amplitude. A situation like this is called resonance. (so would that mean in resonance the amplitude is always increasing?)
    yeah?:unsure:
    Wouldn't resonance cause maximum displacement/amplitude as well....
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    if the driving frequency of an oscillating object matches the natural frequency, maximum energy transfer takes place and hence the amplitude is maximum. The driving force does the work on the object which is the source of energy. When the amplitude is maximum that is driving frequency equal to or very close to the natural frequency, the phenomenon is called resonance.

    at dimi3, I think you have got it right.
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    (Original post by dimi3)
    sorry about all the posts but help me please :woo:
    so this is how i understand resonance, tell me if i got anything wrong
    If the driving frequency of an object matches its natural frequency, it will absorb more energy (this is because were supplying it with energy right?), increasing its amplitude. A situation like this is called resonance. (so would that mean in resonance the amplitude is always increasing?)
    yeah?:unsure:
    Resonance is when the driving frequency matches the natural frequency, forcing it to oscillate at it's maximum amplitude. The amplitude should, theoretically, just increase to the max and then go down, but in reality, it increases over time...
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    umm why should it go back down again? i mean theoretically?
    so the amplitude keeps increasing as long as the driving force is still there right? If the driving force is removed, theoretically it should keep oscillating at the same amplitude right? but because of air resistance and stuff it decreases? i feel like im getting it now XD
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    someone help!!!
    Just started practising after chem5 and got about 4 hrs left.
    In the specimen paper mcq 3, why is the time always bouncing between -ve and +ve and how is it done?
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    (Original post by lefneosan)
    Hi does anyone know if there is any interaction between white dwarfs and red giants? e.g. main sequence become red giants which then become white dwarfs?
    Book says that when the fusion of heavier nuclei (what type of nuclei?) stops (in red giants), the star cools and shrinks to a white dwarf.

    But dunno, just touched on astronomy 1st time an hour ago.
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    i wanted to ask the same question too... in multiple choice question 3..? whats the answer and how do we get it?
    whats the point in them reversing the axes
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    (Original post by dana.h)
    i wanted to ask the same question too... in multiple choice question 3..? whats the answer and how do we get it?
    whats the point in them reversing the axes
    (Original post by obviouslystudying)
    someone help!!!
    Just started practising after chem5 and got about 4 hrs left.
    In the specimen paper mcq 3, why is the time always bouncing between -ve and +ve and how is it done?
    The question's wrong. The axes-labels should be the other way around - so that displacement is on the y and time on the x. So, the child's not swinging through time.

    In order to get the answer, you use:

    v= Awsinwt
    since it's at a max, sinwt=1
    so v=Aw

    in order to get w , we use:
    T = 2pi/w
    w = 2pi/T

    from the graph: (assuming the numbers are correct)
    T=3
    therefore, w = 2/3pi

    and A= 1.5

    so v = 1.5*2/3pi

    which = pi.
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    (Original post by dimi3)
    umm why should it go back down again? i mean theoretically?
    so the amplitude keeps increasing as long as the driving force is still there right? If the driving force is removed, theoretically it should keep oscillating at the same amplitude right? but because of air resistance and stuff it decreases? i feel like im getting it now XD
    Well, if the frequency changed, then it'll decrease - I forgot to put that! :p:

    Yay!
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    (Original post by unamed)
    The question's wrong. The axes-labels should be the other way around - so that displacement is on the y and time on the x. So, the child's not swinging through time.

    In order to get the answer, you use:

    v= Awsinwt
    since it's at a max, sinwt=1
    so v=Aw

    in order to get w , we use:
    T = 2pi/w
    w = 2pi/T

    from the graph: (assuming the numbers are correct)
    T=3
    therefore, w = 2/3pi

    and A= 1.5

    so v = 1.5*2/3pi

    which = pi.

    now its perfect .. another question how do i know when to use cos or sin for getting displacement?
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    edexcel blue book. page 188 . about astronomical distances

    in thw worked example, we have been asked to find distance of the star from the earth. so why have they given distance between sun and the star??? surely its NOT the same thing!!
 
 
 
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