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    (Original post by cowie)
    oh right, didn't see the A*AA for camb oops.. You reckon you can do that ey?
    Thankfully I only need AAB for Architecture at UCL which means I don't need to stress all too much
    Well A* in FM is a bit of a worry, but oh well, can't complain (one of the FM exams is just under 2 months!!)
    Yay! But still, good luck with your exams
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    Hey guys does anyone know how to get access to the 2015 papers for physics unit 4, or all of them?. My physics teacher cant access them and we didn't have a mock this year.
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    Yep, they've been attached
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  1. File Type: pdf AQA-PHYA4-1-QP-Jun15 (3).pdf (827.6 KB, 741 views)
  2. File Type: pdf AQA-PHYA4-2-QP-Jun15 (2).pdf (602.1 KB, 625 views)
  3. File Type: pdf AQA-PHYA4-2-Final-MS-Jun15-v1.1 (1).pdf (132.5 KB, 176 views)
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    (Original post by cosmicapple)
    Yep, they've been attached
    <3
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    Do we need to know about the experiments for determining the value of the specific heat capacity? It doesn't say we need to on the specification but its been given 3 pages on the nelson thrones book.
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    (Original post by cosmicapple)
    Do we need to know about the experiments for determining the value of the specific heat capacity? It doesn't say we need to on the specification but its been given 3 pages on the nelson thrones book.
    They're just examples. But AQA can most certainly use one of the this examples and ask you to apply your knowledge
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    (Original post by cosmicapple)
    Do we need to know about the experiments for determining the value of the specific heat capacity? It doesn't say we need to on the specification but its been given 3 pages on the nelson thrones book.
    (Original post by kingaaran)
    They're just examples. But AQA can most certainly use one of the this examples and ask you to apply your knowledge
    Our teacher usually asks us to 'Describe an experiment to determine....' in his tests, and I suspect that these are past exam questions. Though I haven't yet looked at any past papers so I couldn't say for sure.

    I think we could be asked to describe an experiment as a high mark question (4+) in the exam

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    (Original post by Euclidean)
    Our teacher usually asks us to 'Describe an experiment to determine....' in his tests, and I suspect that these are past exam questions. Though I haven't yet looked at any past papers so I couldn't say for sure.

    I think we could be asked to describe an experiment as a high mark question (4+) in the exam

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    I did a unit 5 paper yesterday and the describe the experiment 6 marker was horrible :'(


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    (Original post by kingaaran)
    I did a unit 5 paper yesterday and the describe the experiment 6 marker was horrible :'(


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    What were you made to find out in the experiment?
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    (Original post by Euclidean)
    What were you made to find out in the experiment?
    You had to weigh up two methods to find the radius of the nucleus, their limitations, their advantages and disadvantages and it was so long! The levels in the mark schemes weren't very forgiving either
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    I'm dreading the A2 physics exams so much I hardly understand it
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    hey guys, is there a unit 5 thread??
    Also is anyone doing Astrophysics as their optional unit???
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    (Original post by boyyo)
    hey guys, is there a unit 5 thread??
    Also is anyone doing Astrophysics as their optional unit???
    http://www.thestudentroom.co.uk/show....php?t=3918125


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    (Original post by jarjarmonkey)
    "4 An electric heater is placed in an insulated container holding 100g of ice at a temperature of -14 degrees C. The heater supplies energy at a rate of 98 joules per second.

    4(a) After an interval of 30s, all the ice has reached a temperature of 0 degrees C.Calculate the specific heat capacity of ice."

    2100 J per kg per K (from E=mc delta T)"

    4(b) Show that the final temperature of the water formed when the heater is left on for a further 500s is about 40 degrees C.
    specific heat capacity of water = 4200 J per kg per K
    specific latent heat of fusion of water - 3.3 x 10^5 J per kg"

    Calculate energy/time to melt ice, then calculate the further change in temperature from the remaining energy/time.

    "4(c) The whole procedure is repeated in an uninsulated container in a room at a temperature of 25 degrees C.State and explain whether the final temperature of the water formed would be higher or low that than calculated in part (b)."

    Can anyone explain why the answer to 4c) is higher
    The water is below 25 degrees for less time than than it is above it. When it is below 25 degrees C the room transfers thermal energy to the water, when above 25 degrees C the water transfers energy to the room/surroundings. Assuming the temperature of the surroundings doesn't change which is a fair assumption given the mass of the surroundings (i.e the air around it) is much more than the mass of water in the beaker.
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    (Original post by Protoxylic)
    The water is below 25 degrees for less time than than it is above it. When it is below 25 degrees C the room transfers thermal energy to the water, when above 25 degrees C the water transfers energy to the room/surroundings. Assuming the temperature of the surroundings doesn't change which is a fair assumption given the mass of the surroundings (i.e the air around it) is much more than the mass of water in the beaker.
    How can the temperature of the water reach above 40 degrees if it starts transferring thermal energy back to the surroundings, when it reaches above room temp. Does the water just gain thermal energy at a really fast rate so it gains about 15 more degrees before transferring it back?
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    (Original post by jarjarmonkey)
    How can the temperature of the water reach above 40 degrees if it starts transferring thermal energy back to the surroundings, when it reaches above room temp. Does the water just gain thermal energy at a really fast rate so it gains about 15 more degrees before transferring it back?
    This question doesn't really have enough information to answer it quantitatively (you'd need a bit more information). I remember this question when I did my A2s. Because you're supplying thermal energy at a constant rate to the water, but you don't know the rate at which thermal energy is being dissipated by the water into the surroundings. There is Newton's law of cooling which states that the rate of thermal energy dissipation by a body is proportional to the difference in temperatures between the body and its surroundings, but this is only approximately true in convective heat transfer which is approximately true for this question.

    To answer the question definitively you'd need to know how fast water dissipates thermal energy to air up to a temperature difference of 15 degrees.

    A way to think about it is that since you're supplying energy for a given interval of time, the temperature gain of the water from 0 to 25 should take less time since there is extra thermal energy input by the surroundings. Any temperature after that (above 25), the net thermal energy input to the water is decreased as the surroundings acts as a sink for thermal energy.

    So an approximate answer would be since the difference in temperatures between 25 and 40 is less than 0 and 25 and so the net thermal energy input should be increased. => Higher final temperature.

    An easier way to think about it is to understand that the surroundings supplies energy to the ice/water all the way from when it is ice to when it reaches 25. Any temperature above that the water does indeed transfer some of its thermal energy to the surroundings, but at a very slow rate (prop to temp difference).
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    (Original post by Protoxylic)
    This question doesn't really have enough information to answer it definitively (you'd need a bit more information). I remember this question when I did my A2s. Because you're supplying thermal energy at a constant rate to the water, but you don't know the rate at which thermal energy is being dissipated by the water into the surroundings. There is Newton's law of cooling which states that the rate of thermal energy dissipation by a body is proportional to the difference in temperatures between the body and its surroundings, but this is only approximately true in convective heat transfer which is approximately true for this question.

    To answer the question definitively you'd need to know how fast water dissipates thermal energy to air up to a temperature difference of 15 degrees.

    A way to think about it is that since you're supplying energy for a given interval of time, the temperature gain of the water from 0 to 25 should take less time since there is extra thermal energy input by the surroundings. Any temperature after that (above 25), the net thermal energy input to the water is decreased as the surroundings acts as a sink for thermal energy.

    So an approximate answer would be since the difference in temperatures between 25 and 40 is less than 0 and 25 and so the net thermal energy input should be increased. => Higher final temperature.
    Thanks for your help
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    Hey guys, is there a website or document that someone can share with me that has all the notes needed and experiments because I feel like I'm missing stuff from my notes


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    Protoxylic hey, I remember you from last year! Will you be putting up the unofficial mark scheme this year?
 
 
 
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