Turn on thread page Beta
    Offline

    0
    ReputationRep:
    that's weird i thought the de broglie question was Just asking the de broglie wavelength of the electrons at that speed. didnt remember or "see" anything about ratio - damn :/ oh well the rest i think went well. thank god i didnt miss out a whole question or anything because all the talk about "ratio" got me panicking!

    what did people get for g on the graph, i got 9.2 - the very first question got me worried for about 10mins lol then i realised you use P=FV
    Offline

    2
    ReputationRep:
    (Original post by xelprep)
    what did people get for g on the graph, i got 9.2
    meltdown initially on that. thought i'd be clever and do my gradient as T2/l and have l in metres. sadly that gave me g=9x103 so i went back and recalculated getting 9.75..... or 9.8 (2sf)
    have to say those two questions were the ones i was least comfortable doing. did the graph question last and somehow managed to finish them after spending 10 mins sitting there like a wally scratching my head staring at 9 dotted lines
    Offline

    0
    ReputationRep:
    (Original post by corkskrew)
    By simply writing in the last line of my derivation without giving a reason, as far as I remember. They in the opposite direction?
    Haha. I just guessed that one was positive. Seeing as though V is measured relative to infinity, I put g as being positive.

    Thinking about it, you need energy to pull an object away from a planet, but g will attract an object. Kinda makes sense that one is positive and one is negative.
    Offline

    2
    ReputationRep:
    ii) I got l0 = 63.5mm. Drew a graph, and got a negative intercept (about -24mm). Splitting the equation into the form y = mx + c gave the equation of the y-intercept to be - 4(pi)2l0/g. Using g = 10000.1 ish mm s-2 will get you a positive value for l0 as the minus signs cancel.
    It was T^2 against length, so surely your intercept should of been a value of T^2 not a length - 24mm.

    Just realised I did this wrong myself :mad:forgot to extend my intercept back to x = 0 and did it at summit like x = 300mm cause of my axis. :mad: :mad:
    Offline

    0
    ReputationRep:
    (Original post by tishysquishy)
    lol, i got a ratio of 1E7:1................ i think that MAY be wrong.... whoopsie
    If you mean E as in exponent, I think your answer is suprisingly close to mine!

    ..not necessarily a good thing though :P

    (Original post by xelprep)
    mr_shoe_uk you just had to use the power value they gave you. use P = FV and divide them
    Didn't remember them giving you a power value, so I guess I did a lot of extra.. Still got 11% though
    • Thread Starter
    Offline

    2
    ReputationRep:
    for the first question i did it the long way round that mr_shoe_uk said, as for the intercept i found c to be 29 or 2.9 or something then subbed it into c=4pisqared lo/g foudn the value of lo and it was -317ish lol. wasn't sure about the -ve and + signs on the g thing just kinda stuck it on at the end! anyway i best go revise for chem ciao
    Offline

    0
    ReputationRep:
    When I got to the couple of questions after I realised I really should have plotted my graph the other way round (I had T2 on the X axis).


    I did the one for working out g by using 1/(gradient of my graph) = 4π2 /g

    Found l0 with some algebra to find when l = 0. Got reasonable answers so I guess they're right. Just hope they'll accept the working cos looking at the mark schemes they seem to be picky about how you work stuff out.


    Filling in the table had me stumped for a while on that question. I read the heading of the last column 'T2/s2' and spent ages looking for s


    Should hopefully be ok! Fortunately can afford to lose a few marks from decent AS marks.




    Completely unrelated but not looking forward to chemistry tomorrow.
    Offline

    10
    ReputationRep:
    (Original post by mr_shoe_uk)
    If you mean E as in exponent, I think your answer is suprisingly close to mine!

    ..not necessarily a good thing though :P

    Well i'm going to blindly trust u to be an amazing physicist so i can feel better bout myself! hehehe

    loadsa peepsicles seem to b doin chem who do phys, i really shud b doing my methods of analysis blah blah di bloody blah....grrr its so boring
    Offline

    10
    ReputationRep:
    (Original post by davedave)
    Filling in the table had me stumped for a while on that question. I read the heading of the last column 'T2/s2' and spent ages looking for s

    AW! thats SOOOOO cute! diddums ..... :p:
    Offline

    0
    ReputationRep:
    (Original post by Dogberry)
    It was T^2 against length, so surely your intercept should of been a value of T^2 not a length - 24mm.

    Just realised I did this wrong myself :mad:forgot to extend my intercept back to x = 0 and did it at summit like x = 300mm cause of my axis. :mad: :mad:
    That's the point. The y-intercept - T2 - was equal to 4(pi)2lo/g.

    Look at the untits of each bit. Multiplying though by g gives s2 mm s-2, and because 4(pi)2 has no units, that gives Io = mm.
    Offline

    0
    ReputationRep:
    (Original post by tishysquishy)
    Well i'm going to blindly trust u to be an amazing physicist so i can feel better bout myself! hehehe

    loadsa peepsicles seem to b doin chem who do phys, i really shud b doing my methods of analysis blah blah di bloody blah....grrr its so boring
    Hehe, thanks. I did get an A at AS (after jan resit of unit 3..) so I don't know :P I'm hoping it did ok, even if we/I did get that one wrong, let's hope we did well overall at least.

    What chemistry exam board are you doing? I've got Edexcel synoptic tomorrow. Done a little revision but don't really know what else to do. IR spec came up in unit 5, with a fairly big question on it, so I only really expect mas spec. and NMR to come up, which are both really "work it out with given information" rather than memorise things.
    Offline

    10
    ReputationRep:
    (Original post by mr_shoe_uk)
    Hehe, thanks. I did get an A at AS (after jan resit of unit 3..) so I don't know :P I'm hoping it did ok, even if we/I did get that one wrong, let's hope we did well overall at least.

    What chemistry exam board are you doing? I've got Edexcel synoptic tomorrow. Done a little revision but don't really know what else to do. IR spec came up in unit 5, with a fairly big question on it, so I only really expect mas spec. and NMR to come up, which are both really "work it out with given information" rather than memorise things.
    Lol i like to think the worst usually so i'm not dissapointed!
    I'm doing OCR (normal one, not salters) We had a huge 'lets figure out what the compound is! (i kinda like those )' for our organic so i have no idea as to what will come up in our mass spec.

    Ours aint all that synoptic (at least i hope not and if so ... someone didnt tell me!) but we need to no trends and patterns of period 3, as well as transition metals grrr. So there is a lot to learn.

    pssst.....is this us trying to do ANYTHING but revise? :P
    Offline

    0
    ReputationRep:
    Hmmm..
    For that graph one i got l0 to be 300mm and g to be 9800 ish mm which seemed ok. plotted it on my calculator and got a similar graph so cant be too bad

    Bring on the results!
    • Thread Starter
    Offline

    2
    ReputationRep:
    g is supposed to be about 9.8 becasue it is g as in gravational field strength you only got 9800 if you forgot to convert the first time u used mm into m
    Offline

    0
    ReputationRep:
    yeh i know i just gave the answer in mm as that was that it started off as.

    I also got around 7-8000Kg as the density of whatever it was.
    Offline

    0
    ReputationRep:
    Could of been a worse exam although I agree about the large questions for little marks. The ratio I got to be larger that 1 - but the 11% etc seemed to correlate. g for the graph i got to be 9.97 which i though was superbly accurate looking at my daft "scales" for the graph where one tiny square was worth 0.8!
    Offline

    0
    ReputationRep:
    how many marks do you lose for significant figures? because a lot of times i just put down 8.0 instead of 7.98 for example and the next question i used the 8.0 instead of the more "accurate" one so that answer is slightly off too. but because i used the same value from previous question i dont lose marks right? :confused:
    Offline

    0
    ReputationRep:
    (Original post by MdSalih)
    Was a pretty good paper - didn't find it to bad.

    As for that last question.. the one about oxygen leaving the planet, I said there would be a surplus of energy after heating it to 400K, so the remaining energy would result in there being KE and therefore motion, which would let it escape into space.

    Or something to that affect.

    MdSalih
    Not quite you worked out the MEAN KE this means some will have more E and some less, hence in the question it said why SOME of the particles could escape not all of them. Bit tricky you see.

    That graph questions was a killer, but other than that OK
    Offline

    1
    ReputationRep:
    I think this was okay... I got 11% for the efficiency, 1 for the ratio.

    For the graph, I got 10000 for g, then released this was in mm/s^2. So I got 10.0 m/s^2.
    For l0, I got 300 mm, then l=550 mm (I think) for the next bit.

    I had 52 minutes spare at the end of the exam. Got really bored. I programmed a game into my graphical calculator, where you have a 0 and have to press up to jump over the 5s that come towards you.
    Offline

    0
    ReputationRep:
    (Original post by davedave)
    When I got to the couple of questions after I realised I really should have plotted my graph the other way round (I had T2 on the X axis).
    The question specifically asked for T2 against l. S marks may be lost if people did l against T2.
 
 
 
Turn on thread page Beta
Updated: July 4, 2005
The home of Results and Clearing

3,069

people online now

1,567,000

students helped last year

University open days

  1. Sheffield Hallam University
    City Campus Undergraduate
    Tue, 21 Aug '18
  2. Bournemouth University
    Clearing Open Day Undergraduate
    Wed, 22 Aug '18
  3. University of Buckingham
    Postgraduate Open Evening Postgraduate
    Thu, 23 Aug '18
Poll
A-level students - how do you feel about your results?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.