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EDEXCEL PHYSICS UNIT 6 > HOW WAS IT? watch

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    im dont know what ur tryin to say...doesnt make sense to me...anyway.. the exam is over now...will just have to wait for the results day to see if we get into our firm choice of uni
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    a lot easier than expected
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    (Original post by mikeA1)
    check this out though :confused:
    i dont quite get wat u'v done...but surely the current wont jus peak like that cuz the transition of the holes is gradual?

    in any case..its 2 marks
    rest ur brain

    exams get over tmrwww :dancing2:
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    i could hav sworn the passage said q was max when area of holes is max.

    im such a muppet, spent the last 30 mins readin over it in boredom and didnt notice my one huge mistake that cocked up the whole of q1

    never mind

    hope u all did ok i thought it was better than it could and should hav been
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    omg **** lol words
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    (Original post by RMIM)
    Well that was the point of the question. The K.E is converted to (Internal energy) heat! - that why the temp goes up.

    What was confusing was the questions after.

    1. Do you expect the real temp rise to be greater or less than the calculated value (well that not it but it was on those lines).

    Well first I though not all the K.E will be turned to heat. Some will be turned into sound. So I thought real value would be less.

    But then I thought of all the ball rubbing against each other. Heat due to friction so I change my mind. (But did write about the sound too).

    2. What would you expect if water was used (again not the real quesrion, but its on those lines)

    Anyway the heat capacity of water is much higher. i would expect the temp rise to be much less. But the question was worth 3marks! what the -
    I said some rubbish about there being more molecules than ball bearings, no idea what that means though.

    Stupid questions!
    Can someone tell us what we should have wrote. I think it was 3marks + 3 marks for the 2 questions.
    I said the real temp rise would be less cos some of the energy goes to heating the plastic tube, and is lost as sound energy, and as energy to the surrounding air.

    For the water thing. I said the shc of water was much higher therefore the temp wouldn't rise as much. but then i said the mass of water was much less (cos they said it was only a few cm^3 which is only a few grams), therefore the temp would rise more. and that the effect due to the smaller mass would outweigh the fact that the shc of water was higher, so in fact the temp of the water would rise by more overall.
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    (Original post by sonja)
    I said the real temp rise would be less cos some of the energy goes to heating the plastic tube, and is lost as sound energy, and as energy to the surrounding air.

    For the water thing. I said the shc of water was much higher therefore the temp wouldn't rise as much. but then i said the mass of water was much less (cos they said it was only a few cm^3 which is only a few grams), therefore the temp would rise more. and that the effect due to the smaller mass would outweigh the fact that the shc of water was higher, so in fact the temp of the water would rise by more overall.
    Oh yes. Did not think of that, We had about 380g of lead no? How much water lets say 20ml, that 20g.

    BUT does the mass not cancel out in the equation? Does not matter if we had an elephant in the tube. (I hope it does as I did not use the mass for that bit. -- can someone verify its correct to cancel the mass)

    Energy is change =mc (delta)T = mgh
    [loss of potential energy is gain in K.E. Loss of K.E to heat]

    c(delta)T =gh (times 60, poor elephant)

    But no mass in the equation. so temp change is dependant on specific heat capacity only.

    Is that correct anyone?
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    (Original post by RMIM)
    Oh yes. Did not think of that, We had about 380g of lead no? How much water lets say 20ml, that 20g.

    BUT does the mass not cancel out in the equation? Does not matter if we had an elephant in the tube. (I hope it does as I did not use the mass for that bit. -- can someone verify its correct to cancel the mass)

    Energy is change =mc (delta)T = mgh
    [loss of potential energy is gain in K.E. Loss of K.E to heat]

    c(delta)T =gh (times 60, poor elephant)

    But no mass in the equation. so temp change is dependant on specific heat capacity only.

    Is that correct anyone?
    yeah i noticed that, but used mass anyway since they had given it
    but i kno wat u mean n i agree.. the mass of the water shouldnt matter

    relax...its over now, exams r FINISHED ...stop worrying!
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    (Original post by RMIM)
    Oh yes. Did not think of that, We had about 380g of lead no? How much water lets say 20ml, that 20g.

    BUT does the mass not cancel out in the equation? Does not matter if we had an elephant in the tube. (I hope it does as I did not use the mass for that bit. -- can someone verify its correct to cancel the mass)

    Energy is change =mc (delta)T = mgh
    [loss of potential energy is gain in K.E. Loss of K.E to heat]

    c(delta)T =gh (times 60, poor elephant)

    But no mass in the equation. so temp change is dependant on specific heat capacity only.

    Is that correct anyone?
    Yeah that is a good point, didn't think of that! Ah well, I did write about the shc so hopefully will only have lost a couple of marks there.
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    I have bn trying to stay away from these subforums as i am happy to have finsihed my exams and kno if i read this thread it will make me feel like i have failed unit 6 - thats what happened with unit45 , i thought i done well after the exams then after seeing the unit45 threads i felt i had flopped

    i hope every found unit 6 gd (not too gd that they pull up the grade boundaries :rolleyes: )

    GD luck for results day

    Sumit
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    (Original post by sumitk87)
    I have bn trying to stay away from these subforums as i am happy to have finsihed my exams and kno if i read this thread it will make me feel like i have failed unit 6 - thats what happened with unit45 , i thought i done well after the exams then after seeing the unit45 threads i felt i had flopped

    i hope every found unit 6 gd (not too gd that they pull up the grade boundaries :rolleyes: )

    GD luck for results day

    Sumit
    phy6 was my worst exam or c4 was. The fact that all the D/C grade people found it ok at my college and some of the A grade peeps found it stupid as there were some good stuff missing that the C/D grade peeps couldn't do at my college.

    All the other past papers the c/d grade peeps would of flopped, but they did ok this time apparently...therefore, the grade boundary may be a bit higher :confused:
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    (Original post by nas7232)
    phy6 was my worst exam or c4 was. The fact that all the D/C grade people found it ok at my college and some of the A grade peeps found it stupid as there were some good stuff missing that the C/D grade peeps couldn't do at my college.

    All the other past papers the c/d grade peeps would of flopped, but they did ok this time apparently...therefore, the grade boundary may be a bit higher :confused:
    i found other papers easier - esp this question 1 , that wasnt easy compared to the simpler stuff in past papers

    hope its 53/80 for an A as it was a few years ago
    its even bn as high as about 77% for an A :eek:
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    (Original post by sumitk87)
    hope its 53/80 for an A as it was a few years ago
    its even bn as high as about 77% for an A :eek:
    Do you mean 77/100 or 77/80 ?
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    (Original post by sumitk87)
    i found other papers easier - esp this question 1 , that wasnt easy compared to the simpler stuff in past papers

    hope its 53/80 for an A as it was a few years ago
    its even bn as high as about 77% for an A :eek:
    it'll be about 76% for an A. I wish it was a really hard paper because i would of got exactly the same mark. For some reason, i'm better at the harder questions :mad:
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    in the SHC one I said that SHC of water >> SHC of lead therefore Delta T will be much smaller. Also said water is more efficient at conducting heat energy due to its molecular structure, and hence less energy will be wasted through sound etc.

    I also put in a somewhat fluffy point saying that some of the water will "cling" to the sides of the test tubes, therefore the actual mass will be lower

    But all in all, Temp rise for water (calculated) would show larger than actual value.
 
 
 
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