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OCR PHYSICS B G491~ 19th May 2015 AM ~ AS Physics Watch

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    (Original post by HennersPD)
    I'm sure the highest frequency was 100kHz not 10kHz?? Thats what i put anyway as it dipped a bit but was still the largest freq. present so i did 100,000 - 100 = 99,900 Hz ~ 100,000Hz?
    I used 10kHz as maximum frequency for speech. I can't actually remember the graph now, but 100kHz seems a little high for the range of human speech given humans can only hear up to 20kHz at the best of times. I could be wrong, though.

    Are you sure you didn't read off the 'Music' blob on the graph?
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    (Original post by ThatPerson2)
    I just assumed that given the idea of a crumple zone is to... well crumple, you would want it to not be very stiff - I mean a material with a YM like A may have a very long plastic region, but it wouldn't work as a 'crumple zone' I therefore thought it would be the one which would crumple most easily, ie the least stiff. I will ask my physics teacher about it and see what he says.
    I totally agree, I put the same sort of thing down. Yeah ask - stick it on here when you have something
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    (Original post by HennersPD)
    I'm sure the highest frequency was 100kHz not 10kHz?? Thats what i put anyway as it dipped a bit but was still the largest freq. present so i did 100,000 - 100 = 99,900 Hz ~ 100,000Hz?
    Also the line went a little into the next barrier
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    (Original post by HennersPD)
    I'm sure the highest frequency was 100kHz not 10kHz?? Thats what i put anyway as it dipped a bit but was still the largest freq. present so i did 100,000 - 100 = 99,900 Hz ~ 100,000Hz?
    I think you may have been looking at the orchestral bit for the 100kHz? As far as I am aware it only went up to 10kHz on the vocal bit (it was quite a bit lower than the orchestral bit, and I don't recall seeing and MHz there). Just from a quick wikipedia: http://en.wikipedia.org/wiki/Voice_frequency (it may be on phones and stuff, but it probably still applies). It only goes up to 3kHz, and if the human voice went to 100kHz then it is a bit lacking?
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    (Original post by ThatPerson2)
    I just assumed that given the idea of a crumple zone is to... well crumple, you would want it to not be very stiff - I mean a material with a YM like A may have a very long plastic region, but it wouldn't work as a 'crumple zone' I therefore thought it would be the one which would crumple most easily, ie the least stiff. I will ask my physics teacher about it and see what he says.
    what is the point of crumpling easily than the people in the car will be in danger as they are exposed more easily, it will have low young modulus and will be tougher which means that it will absorb a very high amount of energy before breaking and it will break plastic-ally So B satisfied both the requirements
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    (Original post by Mik3yMcFly001)
    I used 10kHz as maximum frequency for speech. I can't actually remember the graph now, but 100kHz seems a little high for the range of human speech given humans can only hear up to 20kHz at the best of times. I could be wrong, though.

    Are you sure you didn't read off the 'Music' blob on the graph?
    oh yeah think i might have done :/ was that the one where it dipped slightly at the end?
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    (Original post by HennersPD)
    oh yeah think i might have done :/ was that the one where it dipped slightly at the end?
    I think so. Even if it is you will probably still get method marks.

    (Original post by Zain.chishty)
    what is the point of crumpling easily than the people in the car will be in danger as they are exposed more easily, it will have low young modulus and will be tougher which means that it will absorb a very high amount of energy before breaking and it will break plastic-ally So B satisfied both the requirements
    I agree with you to an extent, but it would still need to crumple to a certain extent (given they don't give data on car crashes it is difficult to know if D would just act like paper and fold in an expose the driver more). If I recall correctly B was the one which had the second steepest incline and then a long plastic region which would imply it is rather stiff. While D doesn't have a very long plastic region it was still second longest (I think) and I would assume that it would be a reasonable trade off. Only way to know is when the real mark scheme comes out I suppose.
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    (Original post by jpetersgill)
    Yeah - and I thought it was a relatively hard paper, not saying I thought I did badly in it


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    Quote 'f off' then 'It was well hard' :P wasnt that what you said? how do you reckon you did then>
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    (Original post by MrPenguinPerson)
    Okay I think I remember what most of the questions were, but not the answers... anyways this might help

    PS, Some of this may be wrong I can't remember completely

    SECTION A
    Q1 Units (3)
    Power AV
    Coulomb - As
    Conductance - AV^-1

    Q2 Refractive Index (2)
    3x10^8/1.7= 1.8x10^8

    Q3 Potential Divider (2)
    3.2 or 4.8 ?

    Q4 Bird Chirrup
    Aspects of Bird Song Wave (2)
    Number of oscillations (2)

    Q5 Waveforms of Sounds
    Logarithmic scale? (1)
    Estimate of highest music frequency (1)
    Estimate of bandwidth of human speech (1)

    Q6 Lenses
    Reading Glasses - Near point/curvature (2)
    Reading Glasses - Minimum power (3)

    Q7 Current Voltage Resistance
    Find average (2)
    Find total charge (2)

    SECTION B
    Q8 Conductance and resistance
    Non- ohmic conductor? (1)
    I think there was a two marker here but can't remember the question (2)
    Find length of wire (3)
    Resistivity ratio (2)
    Temperature increase effect on resistivity (3)

    Q9 Materials
    YM Graphs (3)
    Calculation of YM (2)
    Alloys and Microscopic Properties (6)

    Q10 Imaging
    Levels=16? (1)
    Size of image (2)
    Size of video (2)
    Magnification (3)
    Resolution (2)
    Another graph (2)
    Graph of AFM (2)
    How image is produced (1)
    From this I reckon I've got about 40/60 minimum to 46/60 maximum, what grade is this likely to be seeing as the gerbil consensus is that it was in fact quite a difficult paper, though relatively easy compared to last year! grade boundaries predictions? has it ever been 45+ for an A? also for the second resistance in the table i got 21.1, do you think they'd accept a range as some people have 20. something? any advice on how to do well in g492, aiming for around 140/150 UMS as already have 58/60 UMS in AS coursework and need 240 UMS total for an A at AS
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    (Original post by ThatPerson2)
    I think so. Even if it is you will probably still get method marks.



    I agree with you to an extent, but it would still need to crumple to a certain extent (given they don't give data on car crashes it is difficult to know if D would just act like paper and fold in an expose the driver more). If I recall correctly B was the one which had the second steepest incline and then a long plastic region which would imply it is rather stiff. While D doesn't have a very long plastic region it was still second longest (I think) and I would assume that it would be a reasonable trade off. Only way to know is when the real mark scheme comes out I suppose.
    Nope B had the third least stiffness and was toughest of all.
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    (Original post by Zain.chishty)
    Nope B had the third least stiffness and was toughest of all.
    There were 4 things, so B was the 2nd stiffest. It may have been toughest, but I would assume it would depend on the compromise between the two - you could have a very stiff material which is very tough that would be rubbish for a crumple zone.
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    hey guys, do you reckon you'll lose marks if you filled in the resistance/power table with values to 2 sig. figs?
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    (Original post by ThatPerson2)
    There were 4 things, so B was the 2nd stiffest. It may have been toughest, but I would assume it would depend on the compromise between the two - you could have a very stiff material which is very tough that would be rubbish for a crumple zone.
    Firstly it was not a very stiff material, its gradient was only a little bit more steep than D, and D was just a stupid answer as D is a brittle material and would break instantly when there is a crash and it would be compressed easily as well due to the crash as it very flexible
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    (Original post by Wolfea)
    For the ratio I think I got 6.6..that's about as much as I can remember
    I really didn't understand that question at all!
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    From this I reckon I've got about 40/60 minimum to 46/60 maximum, what grade is this likely to be seeing as the gerbil consensus is that it was in fact quite a difficult paper, though relatively easy compared to last year! grade boundaries predictions? has it ever been 45+ for an A? also for the second resistance in the table i got 21.1, do you think they'd accept a range as some people have 20. something? any advice on how to do well in g492, aiming for around 140/150 UMS as already have 58/60 UMS in AS coursework and need 240 UMS total for an A at AS
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    (Original post by Zain.chishty)
    Firstly it was not a very stiff material, its gradient was only a little bit more steep than D, and D was just a stupid answer as D is a brittle material and would break instantly when there is a crash and it would be compressed easily as well due to the crash as it very flexible
    I can see we have a bit of a disagreement here. I would say it could be either D or B, as D has stiffer (so would not crumple as easily) but tougher (so would absorb more energy before fracturing) and B is less stiff (so crumples easier) but not as tough (so would fracture easier). To be honest, I am unsure of which it is. I mean, if you look at pictures of car crashes it is pretty obvious that the crumple zones have fractured, and all literature on crumple zones I have read refers only to stiffness, but I see your point. All I know is that I put D, so either it is right in which case yay, or it is wrong in which case I can improve for next time.
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    (Original post by HennersPD)
    I'm sure the highest frequency was 100kHz not 10kHz?? Thats what i put anyway as it dipped a bit but was still the largest freq. present so i did 100,000 - 100 = 99,900 Hz ~ 100,000Hz?
    Haha that's what I though and got really worried when other people were saying otherwise. Either we're both right or we both misread :P
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    (Original post by ThatPerson2)
    0.018m is 1.8cm - think of the size of a bulb and the filament inside of it seems likely. I got 0.018m and rounded it to 0.02 (I generally do 2dp or 3sf) do you think this will count against me? I had 0.018m in the working.
    Hm, yeah, also, seeing as lots of people seem to have got the same answer, maybe it's right (fingers crossed!!)

    I can't say for certain, but I imagine that would be okay, especially since you had the answer to a greater precision in your working
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    Oh this is the Crumple zone question? I opted for C, I believe - the straight line one, as it shows that as it comes under increasing stress it crumples uniformly, with uniform strain as it stretches/contracts on itself. Is my physics wrong somewhere here?
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    (Original post by HennersPD)
    So did you get 4.8D for the power as u was negative?
    No I went with 3.2D in the end
 
 
 
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