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OCR Physics B - G491 (Physics in Action) January 2012

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    I thought it was a decent paper compared to any of the previous ones. Perhaps slightly higher grade boundaries too, 45 for an A?

    At times there was a tricky question thrown in but largely straight forward one.

    (Original post by TamsynJoll)
    What did people write for the Steel Question: 'Name a property of this material that makes it suitable for this purpose'
    I wrote Tough because of its ability to absorb energy before it breaks.
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    (Original post by TamsynJoll)
    What did people write for the Steel Question: 'Name a property of this material that makes it suitable for this purpose'
    I went for stiff, because you don't want wobbly buildings

    What reason did everyone put for why they wouldn't let the stress in the cable (on the crane question) exceed 1/3 of the yield stress? I ended up sort of explaining the fact that at the yield stress it would permanently deform, but the 1/3 threw me off a bit, unless they were just being extra safe :/
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    (Original post by Joel R)
    I went for stiff, because you don't want wobbly buildings

    What reason did everyone put for why they wouldn't let the stress in the cable (on the crane question) exceed 1/3 of the yield stress? I ended up sort of explaining the fact that at the yield stress it would permanently deform, but the 1/3 threw me off a bit, unless they were just being extra safe :/
    Same, i ended up just explaining what Yield Stress is in the end =/
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    (Original post by Joel R)
    I went for stiff, because you don't want wobbly buildings

    What reason did everyone put for why they wouldn't let the stress in the cable (on the crane question) exceed 1/3 of the yield stress? I ended up sort of explaining the fact that at the yield stress it would permanently deform, but the 1/3 threw me off a bit, unless they were just being extra safe :/
    I went for flexible, as it was a steel cable so it bends rather than breaking.

    For the 1/3 I put so it isn't accidentally overloaded and causes huge damage.
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    (Original post by Joel R)
    I went for stiff, because you don't want wobbly buildings

    What reason did everyone put for why they wouldn't let the stress in the cable (on the crane question) exceed 1/3 of the yield stress? I ended up sort of explaining the fact that at the yield stress it would permanently deform, but the 1/3 threw me off a bit, unless they were just being extra safe :/
    For the property, I went with Elastic as the steel would need to return to it's original dimensions after being acted on by the Stress/Strain.
    For the 1/3 bit.. I wrote the same.. Just saying that Yield Stress was the maximum Stress the material could undergo before Plastic Deformation. However I was also stumped by the 1/3, therefore just assumed that it would need to be a value smaller than the Yield Stress, so just justified it for being 1/3.
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    I wrote down that because of the dislocations in metals, they are actually much weaker so therefore don't put more than 1/3 of yield stress. Not sure though.
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    Hope the grade boundaries aren't too high.

    Overall the exam had nicer questions to previous past papers.
    Did you lot get 181 for the magnification one?
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    Did anybody else sit this?

    anybody happen to have a mark scheme? Thanks
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    Paper was actually OK, for the wire property, I put ductility, because you dont want the wire to loose its strength when stretched / bent. Though looking it up i'm pretty sure thats wrong
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    (Original post by TamsynJoll)
    What did people write for the Steel Question: 'Name a property of this material that makes it suitable for this purpose'
    It's ductile so it can be made into the cables.
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    Anyone prepared to bring together a lil mark scheme,just as a check on how we did?
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    (Original post by Joshcad)
    Paper was actually OK, for the wire property, I put ductility, because you dont want the wire to loose its strength when stretched / bent. Though looking it up i'm pretty sure thats wrong
    I put ductile not ductility, since you would want to be able to form the metal into wires without losing their strength. Why do you think it is wrong, it seems like the best answer personally.
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    (Original post by asif1995malik)
    Hope the grade boundaries aren't too high.

    Overall the exam had nicer questions to previous past papers.
    Did you lot get 181 for the magnification one?
    The only magnification question I can remember is the one about the tennis ball (which was a value below 1), so I hope you're not on about that one
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    (Original post by Joel R)
    The only magnification question I can remember is the one about the tennis ball (which was a value below 1), so I hope you're not on about that one
    My value for that magnification question was also below 1, If i recall correctly. (Simply through the equation of u=v/m where therefore m=v/u)
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    (Original post by Matt G)
    I put ductile not ductility, since you would want to be able to form the metal into wires without losing their strength. Why do you think it is wrong, it seems like the best answer personally.
    A property of steel isn't ductile, its the dutility ( im sure though that doesn't matter). I was just thinking because its asks for properties of the steel WIRES, not just the steel, and the steel has already been drawn into wires. Oh ,but i guess it stretches more when a load is added to it, drawing it into a thinner wires, so ductility is important. Sounds like its probably right then.
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    I'm sure there'll be numerous correct answers for that question, in the mark scheme.
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    (Original post by KING2011BOB)
    See for the EMF q you had to use the graph to find what voltage you get at 70 degrees-3.7 v so you need 2.3 v across the other resistor
    The 800=69% of the voltage so I did 800/69 * 39 = 511 ohms

    I think around 41-42 marks for an A is reasonable for this paper tbh
    in our class half of us did your way and the other did a different way. I ended up doing what you did finding 2.3V across other resistor , and as we had the resistance and V across one resistor , i worked out the current as it is the same across both components (series circuit) , then knowing V for both , i worked out R for the resistor which the resistance we were not given and got something like 1300 ohms ??
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    what did everyone get for the different types of image altering and what did you put that the processed image was?

    The magnification value was >1 right? cuz it threw me as i was looking for the diameter of the image of the ball :L then realized the lengths cuz be useful
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    (Original post by MrMeep2580)
    what did everyone get for the different types of image altering and what did you put that the processed image was?

    The magnification value was >1 right? cuz it threw me as i was looking for the diameter of the image of the ball :L then realized the lengths cuz be useful
    Magnification was definitely <1, as it was focused onto a smaller screen than the object it was capturing.

    Oh, and I've just realised our confusion with the steel's properties. I'm pretty sure they actually said:
    "Steel is used in girders in buildings. Steel is strong. State one other property of steel that makes it suitable for this purpose".

    There just happened to be more than one question involving steel
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    (Original post by MrMeep2580)
    what did everyone get for the different types of image altering and what did you put that the processed image was?

    The magnification value was >1 right? cuz it threw me as i was looking for the diameter of the image of the ball :L then realized the lengths cuz be useful
    Wasn't the mag - 0.05/10?

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