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

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    Hi! It says in the spec for materials section we need to know "direct evidence of the size of particles and their spacing" Probably being stupid but what is this!?! Also what equations do we need to know for materials that aren't on the formula sheet? Thanks so much!


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    (Original post by yeslordsugar)
    Hi! It says in the spec for materials section we need to know "direct evidence of the size of particles and their spacing" Probably being stupid but what is this!?! Also what equations do we need to know for materials that aren't on the formula sheet? Thanks so much!


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    I think that means they can give you an electron microscope view and some dimensions and you have to work out the size of the atoms, etc.


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    (Original post by jpetersgill)
    how do people approach significant figures for this exam?
    Slowly and with caution, trying not to startle them. Then I shove a bag over their head, from behind.
    Bruv
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    (Original post by jpetersgill)
    I think that means they can give you an electron microscope view and some dimensions and you have to work out the size of the atoms, etc.


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    like they did last year with the graphene layer
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    (Original post by jpetersgill)
    how do people approach significant figures for this exam?

    Usually if a question contains numbers with 2sf, then I put my answer in 2sf. Even if it doesnt i think 2sf is always a good bet, but i don't think it matters too much as long as you do whatever significant figures correctly.
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    (Original post by HennersPD)
    I'm resitting also and wondered if anyone has done the g491 paper from may 2014 and what they thought about the lenses questions as these confused me! Also do you think this years paper will be easier or not? Is this the last year for the G492, G494 AND G495 papers?

    Tell me about it. And that nonsense with the QR code...so many questions were too unrelated. Like someone else said I think it could be easier as last year caused a lot of complaint. However, I do believe this is the final year of this spec so they could make it even harder...who knows.
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    (Original post by MJS107)
    Tell me about it. And that nonsense with the QR code...so many questions were too unrelated. Like someone else said I think it could be easier as last year caused a lot of complaint. However, I do believe this is the final year of this spec so they could make it even harder...who knows.
    i didn't even get onto the qr code question since i got so stunned by the potential divider question haha!
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    (Original post by MJS107)
    Tell me about it. And that nonsense with the QR code...so many questions were too unrelated. Like someone else said I think it could be easier as last year caused a lot of complaint. However, I do believe this is the final year of this spec so they could make it even harder...who knows.
    Did people complain formally to the exam board or you mean just general complaining on TSR? If the complaints were sent to the exam board, then I guess they could make it easier otherwise it would seem ignorant of them.
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    (Original post by SheLikeTheMango)
    Did people complain formally to the exam board or you mean just general complaining on TSR? If the complaints were sent to the exam board, then I guess they could make it easier otherwise it would seem ignorant of them.
    There were several official complaints to OCR via email and letter but most received the same generic response from OCR basically saying there was nothing wrong with exam itself just that some people struggled on the timing due to the length of some harder questions!! So I hope they make the exam easier this year for the sake of those resitting who had to endure last year's horrific exam :/
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    (Original post by HennersPD)
    There were several official complaints to OCR via email and letter but most received the same generic response from OCR basically saying there was nothing wrong with exam itself just that some people struggled on the timing due to the length of some harder questions!! So I hope they make the exam easier this year for the sake of those resitting who had to endure last year's horrific exam :/
    We can only hope, this exam is before Maths and chemistry, so i need a good exam to get me going

    Btw how is A2 physics and what other subjects do you take ?
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    How's everyone feeling for the exam ?
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    (Original post by SheLikeTheMango)
    We can only hope, this exam is before Maths and chemistry, so i need a good exam to get me going

    Btw how is A2 physics and what other subjects do you take ?
    I do Maths, Chemistry and Physics! It's funny I actually find A2 physics much easier than AS!
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    2 more days people!
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    (Original post by jpetersgill)
    how to people approach significant figures for this exam?
    If it doesnt ask to leave the answer to a certain amount of significant figures or decimal places, I pretty much always do it to 2 or 3 significant figures. But it depends on what numbers you're dealing with. I use whatever seems most appropiate for the numbers in use. For example if you were finding current from 230 resistance and 30V. 30/230 = 0.130434...7
    what I would do here is look at the data given and see what has the most significant figures, which is 230 with 3 significant figures. So I would therefore leave the answer to 3 s.f. which would be 0.13A
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    leave the answer to 3 s.f. which would be 0.13A
    0.130A no? :O
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    (Original post by IrfanR)
    0.130A no? :O
    0.13 is the same as 0.130. I prefer to keep it without the unwanted 0 as it looks nicer lol.
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    Oh, I thought the 0 was to be included otherwise it's 2 significant figures
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    http://www.ocr.org.uk/Images/175463-...-in-action.pdf

    Could someone go through 9a to the end of 9b with full working out pls?
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    To anyone who needs it, the June 2014 G491 paper and mark scheme is attached.
    Attached Images
  1. File Type: pdf g491_jun14.pdf (206.2 KB, 208 views)
  2. File Type: pdf g491_ms_jun14.pdf (235.9 KB, 188 views)
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    (Original post by IrfanR)
    http://www.ocr.org.uk/Images/175463-...-in-action.pdf

    Could someone go through 9a to the end of 9b with full working out pls?
    9a) 1Mbyte*1000*3 = 3072. Remember 1Mbyte is actually 1.024 not exactly 1.
    Now do 3072/3500 to get 0.878, which is <1Mbyte.

    ii) This is all about estimating, which you need a rough idea based on events in your own life to make an accurate judgement. The first box is about pages per book, which from my experience tends to be around 300 pages, the second box to fill in is words per line, which I would roughly say is 15. Now you use your estimates to find an answer. It states that 1 byte = 1 character which there is 6 of per word. So 6*15*30*300 = 810,000 bytes of information. Remember this isn't the exact answer, the answer will depend on YOUR estimates. There tends to be a range of answers, so you should be good as long as your estimates are reasonable.

    9b) Firstly, convert minutes to seconds so it doesnt throw you off later. And be careful with this question, it asks for the answer to be in BITS per second. We were dealing with bytes earlier, so 1 bytes = 8 bits. Now, we use the answer from part ai) which is the information per book. 0.878Mbytes * 10^6 to get it into bytes, then * 8 to get it into bits. This will equal 7,024,000 now we divide this by 60 to get bits per second. 7,024,000/60 = 117067. Keep it to low s.f. and use standard form for big numbers. I got 1.17*10^5 bits/s.

    ii) f = v / λ so plug in the numbers, 3*10^8/0.36 = 8.3*10^8Hz

    iii) not really sure on this one, I guess just look and see what the mark scheme says?


    Hopefully I helped and explained things
 
 
 
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