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Official Thread For OCR Physics A G484 Jan 2011

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So not ready for this exam tomorrow!!! :s

Just wondering if any one can help by explaining how to find the specific latent heat, I know how to do SHC but not latent heat.
And what do we need to know about Brownian motion,
And what’s the N2L experiment, never even looked at this in class.

Thank you in advanced!!!!

PS - What do people think will come up tomorrow?
Original post by jamielollypop
So not ready for this exam tomorrow!!! :s

Just wondering if any one can help by explaining how to find the specific latent heat, I know how to do SHC but not latent heat.
And what do we need to know about Brownian motion,
And what’s the N2L experiment, never even looked at this in class.

Thank you in advanced!!!!

PS - What do people think will come up tomorrow?


Latent heat is the heat energy that brings about a change of state while at a constant temperature - say you add energy to melt ice. There are two kinds you need to know, but they're very similar:

The specific latent heat of fusion is the energy required per unit mass to change a solid to a liquid at constant temperature (this'll be the melting point).
The specific latent heat of vaporisation is the energy required per unit mass to change a liquid to a gas at constant temperature (this'll be the boiling point).

The equation for both is just E=mL, where L is the specific latent heat of fusion/vaporisation. Alternatively, if you're given information about the internal energy of eg. ice at 0 degrees and water at 0 degrees, the latent heat of fusion will just be the difference between them since all the energy difference is made up by the phase change.

Brownian motion is the random movement of particles. If we're asked anything about it, it'll be an experiment to demonstrate it:



The light allows us to see the smoke particles through the microscope. We'll see them moving in a random, zigzag manner, because of the different numbers of 'air particles' striking each smoke particle at different sides and with different directions - this creates a resultant force on the smoke particle, so we see it moving around randomly. Note that we see the effect of the air on the smoke - this is what shows Brownian motion, not just the smoke particles!

I posted a quick explanation of a Newton's second law experiment last page, look for the linear air track. :wink:

I'm going to stop stalking this thread now.
Original post by jamielollypop
So not ready for this exam tomorrow!!! :s

Just wondering if any one can help by explaining how to find the specific latent heat, I know how to do SHC but not latent heat.
And what do we need to know about Brownian motion,
And what’s the N2L experiment, never even looked at this in class.

Thank you in advanced!!!!

PS - What do people think will come up tomorrow?


You only need to find out how to find the Specific Heat Capacity, Not Latent Heat of Fusion or Vaporisation. On the spec it says describe the latent heat of fusion / vaporisation nothing further than that. I wouldn't worry too much about it.

Brownian Motion refers to the chaotic motion of gas molecules. This can be seen when smoke is introduced into a small glass container, which is well illuminated by a source of light. When viewed through a microscope, the molecules can been seen moving in a shuddering motion.

what the hell is N2L ?
Reply 123
Avatar for Ralphus J
Ralphus J
Ok ignore N2L it stood for NEWTONS SECOND LAW ok..

lol:biggrin:
gradee boundaries june 10 ? anyone ? :smile:
Reply 125
Avatar for Selmz
Selmz
can anyone suggest what topics to revise more or predict what questions that might come up? that would be very helpful indeed :smile:
Good luck everyone!! I have a feeling brownian motion will be coming up, revise that xD .
Reply 127
Avatar for Ralphus J
Ralphus J
^ Thanks, its not a very big mark question is it like it wouldnt be .. a 8 marker thing or anything?
Original post by Ralphus J
^ Thanks, its not a very big mark question is it like it wouldnt be .. a 8 marker thing or anything?


wouldn't be a huge one like describing shc experiments, but it'll be worth a fair few i think.
Reply 129
Avatar for Ralphus J
Ralphus J
Original post by nikkijones27
wouldn't be a huge one like describing shc experiments, but it'll be worth a fair few i think.


Ok thanks :smile: good luck! what are the usual grade bounderies roughly?
Original post by Ralphus J
Ok thanks :smile: good luck! what are the usual grade bounderies roughly?


good luck to you too! i really don't know, they've changed by about four marks from last year. weird. i think over 80% and you've safely got an A.
Original post by Ralphus J
Ok thanks :smile: good luck! what are the usual grade bounderies roughly?


http://www.ocr.org.uk/download/admin/ocr_47951_admin_mk_grd_bound_jun_10.pdf

June's. Fairly average.
Straight forward paper but i didn't realise

I LEFT THE ****ING LAST PAGE OUT, DIDN'T REALISE UNTIL I HANDED IT IN - LOOKED LIKE AN EASY 5 MARKS TOO

but all else seemed ok.
Whew.
Finished with about 5-10 mins to spare.
Initially bricking it, but I thought that was quite a nice exam, MUCH Better than the chemistry or biology this jan.
How'd you lot find it?
BTW did you get 1499kg as the mass of the helicopter? That seems quite light... :s-smilie:

EDIT: unlucky to the guy above!
Original post by rishmiester
Whew.
Finished with about 5-10 mins to spare.
Initially bricking it, but I thought that was quite a nice exam, MUCH Better than the chemistry or biology this jan.
How'd you lot find it?
BTW did you get 1499kg as the mass of the helicopter? That seems quite light... :s-smilie:

EDIT: unlucky to the guy above!


I got 1467 kg, which is dependant if you used your value for mass of air, or theirs.

1.5 tonnes is quite reasonable for a helicopter, so yeah.
(edited 13 years ago)
That didnt go too well, I couldnt get the second radius for satellite to work.
What did you get for the first one? 6.4x10^6?
Original post by In the looney bin
I got 1467 kg, which is dependant if you used your value for mass of air, or theirs.

1.5 tonnes is quite reasonable for a helicopter, so yeah.


Phew!
velocity of oxygen molecule: 450?
Reply 137
Avatar for HRM-24
HRM-24
5
Hey yeah okay paper, kilowatt-hour wasn't strictly this spec though. I has mass at about 1400kg though it was a bit light. :smile:
How did people draw the milk graph??
Original post by Oh my Ms. Coffey
That didnt go too well, I couldnt get the second radius for satellite to work.
What did you get for the first one? 6.4x10^6?


6400km seems like the radius of the earth.
I got 2.0 10^7 m, or summin like that

Original post by HRM-24
Hey yeah okay paper, kilowatt-hour wasn't strictly this spec though. I has mass at about 1400kg though it was a bit light. :smile:
How did people draw the milk graph??


True that :smile:
negative gradient straight line going from 18 to 0, then horizontal line for a bit, then steeper negative gradient line going down till -18. u?
(edited 13 years ago)
Reply 139
Avatar for HRM-24
HRM-24
5
Original post by rishmiester
6400km seems like the radius of the earth.
I got 2.0 10^7 m, or summin like that



True that :smile:
negative gradient straight line going from 18 to 0, then horizontal line for a bit, then steeper negative gradient line going down till -18. u?


Steep grad from 18 to 0, then less steep under 0 10 -18.

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