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Physics Questions / Tips

  • 15-06-2007 1:15am
    #1
    Closed Accounts Posts: 23


    How might you find an APPROXIMATE value of the focal lenght? (focal lenght of concave mirror mock question)

    Also does anyone think it likely that all three experiments -
    Concave Mirror
    A proportional to F
    Specific Heat Capacity
    - could be asked - none of them have come up so far

    Tips: Wheatstone bridge, doppler effect, simple harmonic motion, optical fibres


«1

Comments

  • Registered Users, Registered Users 2 Posts: 3,979 ✭✭✭mp3guy


    capslocked wrote:
    How might you find an APPROXIMATE value of the focal lenght? (focal lenght of concave mirror mock question)

    Page 21 of your physics book...


  • Registered Users, Registered Users 2 Posts: 929 ✭✭✭sternn


    Would you say there is a slim chance of the stuff that came up last year in full questions comming up this year?
    So I could probably get away with having a vague knowledge of what came up last year??


  • Registered Users, Registered Users 2 Posts: 3,979 ✭✭✭mp3guy


    sternn wrote:
    Would you say there is a slim chance of the stuff that came up last year in full questions comming up this year?
    So I could probably get away with having a vague knowledge of what came up last year??


    Maybe, sometimes questions come up two years in a row. You could learn most of it over the weekend. Got back through the last 5 years and check the pattern.


  • Registered Users, Registered Users 2 Posts: 1,152 ✭✭✭carlowboy


    sternn wrote:
    Would you say there is a slim chance of the stuff that came up last year in full questions comming up this year?
    So I could probably get away with having a vague knowledge of what came up last year??


    Its very doubtful, there's too much stuff that could come up in long questions that hasn't been asked yet.


  • Registered Users, Registered Users 2 Posts: 929 ✭✭✭sternn


    sternn wrote:
    Would you say there is a slim chance of the stuff that came up last year in full questions comming up this year?
    So I could probably get away with having a vague knowledge of what came up last year??

    Sorry, what i mean to say is: Could i almost completely ignore the stuff that came up last year and know everything else?


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  • Closed Accounts Posts: 7,794 ✭✭✭JC 2K3


    Judging by Irish 2, English 2 and History - no.


  • Closed Accounts Posts: 158 ✭✭madgal


    I would go by what came up in the pre.

    So far paper 2 of Irish covered most of what came up in the pre, and so did the french paper as well.


  • Registered Users, Registered Users 2 Posts: 1,152 ✭✭✭carlowboy


    Sternn- I really doubt it. There's some stuff they love asking every year. (short questions and modern physics)


  • Closed Accounts Posts: 158 ✭✭madgal


    Chapter 29 --- Xrays! I spent 3 hours learning that in evening study one night ... and it comes up every year ... its like a definite question!


  • Registered Users, Registered Users 2 Posts: 1,152 ✭✭✭carlowboy


    madgal wrote:
    Chapter 29 --- Xrays! I spent 3 hours learning that in evening study one night ... and it comes up every year ... its like a definite question!


    Aye, love the X-Rays myself. There's not much in it, so its a simple enough question. If you know your diagram for the production of X-Rays you're set and medical and industrial applications.


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  • Registered Users, Registered Users 2 Posts: 256 ✭✭Turnip2000


    Theres so much choice in physics but the biggest problem i find is that the stuff you know comes up in questions with the stuff you don't know!!:mad:

    Its all about choosing the right Q's, And ye i think they repeat theme selfs alot! Well i hope they do anyway!


  • Closed Accounts Posts: 158 ✭✭madgal


    I just don't understand Einsteins part of the thing ... why was the guy such a genius ... and why was I such a dumbass?!?


  • Closed Accounts Posts: 1,504 ✭✭✭Nehpets


    I know what you mean TurnipFace!


  • Closed Accounts Posts: 1,504 ✭✭✭Nehpets


    madgal wrote:
    I just don't understand Einsteins part of the thing ... why was the guy such a genius ... and why was I such a dumbass?!?

    What part? (not that I'll be able to answer, but I'm sure someone else might be able to :D)


  • Registered Users, Registered Users 2 Posts: 2,312 ✭✭✭Limerick Dude


    Nehpets wrote:
    What part? (not that I'll be able to answer, but I'm sure someone else might be able to :D)


    e=mc squared......

    energy = mass by the speed of light squared....

    Pretty easy equation ;)


  • Closed Accounts Posts: 1,504 ✭✭✭Nehpets


    e=mc squared......

    energy = mass by the speed of light squared....

    Pretty easy equation ;)

    Who asked for that?


  • Registered Users, Registered Users 2 Posts: 256 ✭✭Turnip2000


    Mass as in the change in mass after the ....watever it is!


  • Closed Accounts Posts: 6,296 ✭✭✭RandolphEsq


    I left out the Sound and Vibrations chapter as well as The Wave Nature of Light. The last few chapters in the book are what Im hoping come up a good bit; all that nuclear stuff and particle physics


  • Closed Accounts Posts: 7,794 ✭✭✭JC 2K3


    I want as much mechanics as possible(1.5 Qs?).

    Questions on Heat are also easy and nice.

    Particle physics should be 56/56, have to go over it though.

    I'd like a full question on EMI also, it looks hard but it's so easy after you just learn it.


  • Registered Users, Registered Users 2 Posts: 1,152 ✭✭✭carlowboy


    Anyone get the feeling there'll be something big on semi-conducters? I've only ever seen them come up in Q12 and that was once.


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  • Registered Users, Registered Users 2 Posts: 909 ✭✭✭WildCardDoW


    It's quite hard to tell what will come up. Just learn it all! :p

    ON another note, does anyone happen to have a list of the questions that have come up previsouly. I.E Pressure was part of Q12. etc.

    I was sure I had a lost like this, but I'll be danged if I can't find it! When I need it most of course, it's got lost in a mess of notes.

    Maybe this was it, nevermind: http://www.skoool.ie/skoool/examcentre_sc.asp?id=2107

    My teacher never gave us any of this stuff, I always had to use teh internets.


  • Registered Users, Registered Users 2 Posts: 2,312 ✭✭✭Limerick Dude


    JC 2K3 wrote:
    I want as much mechanics as possible(1.5 Qs?).

    Questions on Heat are also easy and nice.

    Particle physics should be 56/56, have to go over it though.

    I'd like a full question on EMI also, it looks hard but it's so easy after you just learn it.


    Whats EMI again? Sometimes the mechanics q6 can be dodgy, like angular velocity, dont like that. Though i find it very easy to derive kepplers law


  • Registered Users, Registered Users 2 Posts: 909 ✭✭✭WildCardDoW


    Hate angular velocity, I can define it, just always muck up the questions to work them out. :p


  • Registered Users, Registered Users 2 Posts: 1,152 ✭✭✭carlowboy


    Whats EMI again? Sometimes the mechanics q6 can be dodgy, like angular velocity, dont like that. Though i find it very easy to derive kepplers law


    Electromagnetic Induction.


  • Closed Accounts Posts: 16 Cipriana


    ye I'd bet on semi conductors and a latent heat one normally comes up


  • Registered Users, Registered Users 2 Posts: 1,269 ✭✭✭cocoa


    Whats EMI again? Sometimes the mechanics q6 can be dodgy, like angular velocity, dont like that. Though i find it very easy to derive kepplers law
    umm, do you mean kepler's law (one p)? and that's not on the course...


  • Closed Accounts Posts: 93 ✭✭microbiek


    cocoa wrote:
    umm, do you mean kepler's law (one p)? and that's not on the course...


    T^2 is proportional to R^3


  • Closed Accounts Posts: 78 ✭✭Feddd


    When the exam is being made out, the short questions are done last (Q5). They are the things that "Didn't get a go" that year and are likley to come up the next year in long Qs. Static elec and doppler are looking good for Longs this year.
    personally, 3 mechanics exps and 5 mechanics long Qs would be sweet. Applies maths ftw!


  • Closed Accounts Posts: 93 ✭✭microbiek


    Feddd wrote:
    When the exam is being made out, the short questions are done last (Q5). They are the things that "Didn't get a go" that year and are likley to come up the next year in long Qs. Static elec and doppler are looking good for Longs this year.
    personally, 3 mechanics exps and 5 mechanics long Qs would be sweet. Applies maths ftw!


    that would hardly happen


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  • Registered Users, Registered Users 2 Posts: 1,958 ✭✭✭Fobia


    cocoa wrote:
    umm, do you mean kepler's law (one p)? and that's not on the course...

    He seems to be correct, actually...

    Leaving Cert Physics Syllabus

    How odd.


  • Registered Users, Registered Users 2 Posts: 1,269 ✭✭✭cocoa


    microbiek wrote:
    T^2 is proportional to R^3

    O_o, calling it "kepler's law" is a bit of stretch, considering there was three laws, and they referred to eliptical orbits, not just circular ones, and you derive a formula, not just that proportion, and nowhere in the syllabus do they call it kepler's law...


  • Closed Accounts Posts: 93 ✭✭microbiek


    cocoa wrote:
    O_o, calling it "kepler's law" is a bit of stretch, considering there was three laws, and they referred to eliptical orbits, not just circular ones, and you derive a formula, not just that proportion, and nowhere in the syllabus do they call it kepler's law...



    ive seen it they do call it that and its sumtin lik T^2=GMm/R^3(4pi^2) is the formula nt sure!!


  • Registered Users, Registered Users 2 Posts: 1,269 ✭✭✭cocoa


    microbiek wrote:
    ive seen it they do call it that and its sumtin lik T^2=GMm/R^3(4pi^2) is the formula nt sure!!
    have a look at fobia's link to the syllabus, nowhere is the word "kepler" in it. You haven't got the formula right, but I think you're thinking of the right thing. Kepler's third law mentions the proportion between T^2 and R^3, not the formula...


  • Closed Accounts Posts: 1,504 ✭✭✭Nehpets


    Feddd wrote:
    When the exam is being made out, the short questions are done last (Q5). They are the things that "Didn't get a go" that year and are likley to come up the next year in long Qs.

    Where did you get that info?


  • Registered Users, Registered Users 2 Posts: 1,152 ✭✭✭carlowboy


    That's not one of Kepler's laws though. What exactly is it called?


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  • Registered Users, Registered Users 2 Posts: 1,269 ✭✭✭cocoa


    carlowboy wrote:
    That's not one of Kepler's laws though. What exactly is it called?
    it is, technically, a very special case of the third law. It's not given a special name in the syllabus, I don't know if it has one, I've always just called it "formula for the period of a satelite (in a circular orbit)"


  • Closed Accounts Posts: 93 ✭✭microbiek


    cocoa wrote:
    have a look at fobia's link to the syllabus, nowhere is the word "kepler" in it. You haven't got the formula right, but I think you're thinking of the right thing. Kepler's third law mentions the proportion between T^2 and R^3, not the formula...

    oh ryt yeah its T62=4pi62R^3/GM you derive it by saying newtons grav equals centripetal force ye its just pat doyle goin into extar detils just sayin that it states t^2 is prop to R^3


  • Closed Accounts Posts: 93 ✭✭microbiek


    motion of a satellite: The moon is a satellite of the earth Keplers 3rd law states that the periodic time squared is proportional to the radius cubed


  • Closed Accounts Posts: 131 ✭✭Tomlowe


    it's keplers third law and its derivation has come up before.


  • Closed Accounts Posts: 93 ✭✭microbiek


    Tomlowe wrote:
    it's keplers third law and its derivation has come up before.

    came up in the mocks


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  • Registered Users, Registered Users 2 Posts: 1,152 ✭✭✭carlowboy


    Tomlowe wrote:
    it's keplers third law and its derivation has come up before.


    They didn't word it as Kepler's law in the question though did they?


  • Registered Users, Registered Users 2 Posts: 1,269 ✭✭✭cocoa


    Tomlowe wrote:
    it's keplers third law and its derivation has come up before.
    no, it's a formula which happens to be very special case of kepler's third law. You don't have to know the law, or have any extra knowledge about the proportion which happens to be contained in the formula.


  • Closed Accounts Posts: 93 ✭✭microbiek


    where can you get all the syllabuses paticularly the engineering one???


  • Closed Accounts Posts: 93 ✭✭microbiek


    cocoa wrote:
    no, it's a formula which happens to be very special case of kepler's third law. You don't have to know the law, or have any extra knowledge about the proportion which happens to be contained in the formula.


    it just works out that way when you let w=2pi/T


  • Registered Users, Registered Users 2 Posts: 1,152 ✭✭✭carlowboy


    cocoa wrote:
    no, it's a formula which happens to be very special case of kepler's third law. You don't have to know the law, or have any extra knowledge about the proportion which happens to be contained in the formula.


    Well its not a very special case. It deals with circular orbits not eliptical ones (which Kepler's 3rd law was about). But most planet's orbit and satellites orbit are very close to circular so it is reasonably argument. Its not relevant at all in comets though.

    You're right though.


  • Registered Users, Registered Users 2 Posts: 1,269 ✭✭✭cocoa


    there's no w in that formula, you don't have to study the link between simple harmonic motion and circular motion. There's no "working out" necessary, the formula is an equation, as it happens everything other than R and T are constant, so they are proportional, simple, but totally unnecessary for the LC course.

    syllabuses


  • Closed Accounts Posts: 93 ✭✭microbiek


    cocoa wrote:
    there's no w in that formula, you don't have to study the link between simple harmonic motion and circular motion.

    syllabuses


    ther is at the start as centripetal f = mw^2R its not w its a greek letter........thanks for the syllabuses


  • Registered Users, Registered Users 2 Posts: 1,269 ✭✭✭cocoa


    microbiek wrote:
    ther is at the start as centripetal f = mw^2R its not w its a greek letter........thanks for the syllabuses
    oh, you mean omega, angular velocity. It's still not in the formula for the period of a satelite, you mean the derivation? I suppose if you do let omega equal that then it works out that R^3 and T^2 are equal, but that's really beside the point...


  • Closed Accounts Posts: 7,794 ✭✭✭JC 2K3


    cocoa wrote:
    there's no w in that formula, you don't have to study the link between simple harmonic motion and circular motion. There's no "working out" necessary, the formula is an equation, as it happens everything other than R and T are constant, so they are proportional, simple, but totally unnecessary for the LC course.

    syllabuses
    syllabi.


  • Registered Users, Registered Users 2 Posts: 1,152 ✭✭✭carlowboy


    JC 2K3 wrote:
    syllabi.

    Thought I'd come across as a pedantic git if I said that :D


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