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PHYA5 ~ 20th June 2013 ~ A2 Physics

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Original post by FloydHead
For the turning points people, what did you all put for the very last question about travelling faster than light? I think I dropped marks on it, even though it was basically a gift marks question :frown:


lorentz factor would equal to 1/0 if you reach speed of light
lorentz factor = infinity
this suggests mass is infinite
this disobeys conservation of energy as it also suggests infinite energy
Reply 1761
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MSI_10
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Original post by sports_crazy
I might have done it wrong. I used the same volume because volume doesnot change unless you assume the volume is the cylinder+atmosphere. Assuming volume is same I got 3.3 mol and multiply with kgmol^-1


Wait so if you used same volume how did you work out the mass? Wouldnt using same volume give same answer previously (130.5 mols times 4.8X10^-2)
Original post by Pinkhead
You actually might get a mark for that. There's technically nothing wrong with it since you used the equation to show that it isn't possible. You probably won't get the second one though since the same question in a legacy paper wanted a mention of kinetic energy.

:eek:
We have the best usernames on TSR :biggrin:


Indeed we do :P

I was hoping for full ums on this one too, for an A*. Ah well.
Original post by MSI_10
Wait so if you used same volume how did you work out the mass? Wouldnt using same volume give same answer previously (130.5 mols times 4.8X10^-2)

PV=nRT
we got new pressure. I used the same volume because volume of cylinder cant change. We got new temperature. I worked out the moles which is equal to 3.3. I multiplied it by 4.8x10^-3.
I might be wrong. What do u think?
Reply 1764
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kvohra
I am envious of all you who said that turning points was easier than core! Every astro paper I have done makes core look like a joke
Original post by Pinkhead
You actually might get a mark for that. There's technically nothing wrong with it since you used the equation to show that it isn't possible. You probably won't get the second one though since the same question in a legacy paper wanted a mention of kinetic energy.

:eek:
We have the best usernames on TSR :biggrin:


I said lorentz factor = 1/0

suggests mass is infinite

which then suggests infinite energy - disobeying conservation of energy law

Do you think this was enough ? :frown: Hope it is, already lost way too many... just realised I ignored doing an asymptote on 1c on the graph also :tongue: How many marks was the graph?>
In the core part... for a second I thought the first question on positron decay was an astrophysics question :tongue:
Original post by sports_crazy
What answer did u get with this. I used a different method and worked out the moles which were 3.3 and times that by 0.048kgmol^-1 and my answer was 0.16kg


I got ~0.17kg by using a method with pV=nRT
what did everyone put for the 6 marker on stationairy waves?? (TURNING POINTS)
Reply 1769
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Namige
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Original post by kvohra
I am envious of all you who said that turning points was easier than core! Every astro paper I have done makes core look like a joke
Well you clearly haven't looked at the applied spec.
Original post by Dorkins
I got ~0.17kg by using a method with pV=nRT


I used PV= nRT, cant remember what I got though, I hope its a correct method though cos I couldnt think of much else..
Original post by jackerharder
what did everyone put for the 6 marker on stationairy waves?? (TURNING POINTS)


Oh I hated that. I didn't write much... just move detector, when no reading it is a node. Then move again this node mark 1/2 wavelength.... then move it again - here's you full wavelength

That's pretty much all I wrote, I hope I got 3/6 marks
Reply 1772
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iLayton
Original post by bugsuper
I got around 3.9 mols which corresponded to 0.166kg - 0.17kg mass


Yep!


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can anyone remember astro questions?
Original post by Dorkins
I got ~0.17kg by using a method with pV=nRT

I hope i only loose 1 mark for rounding error because I got 0.16.
Reply 1775
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iLayton
Original post by MSI_10
3 marker on why high temperature needed for fusion to occur at star.. What did you put?


High energy is needed so the nuclei can over come electrostatic repulsion... High temp relates to large KE... Something along those lines?


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Original post by posthumus
Oh I hated that. I didn't write much... just move detector, when no reading it is a node. Then move again this node mark 1/2 wavelength.... then move it again - here's you full wavelength

That's pretty much all I wrote, I hope I got 3/6 marks


Ye I wrote that, I also said that nodes formed when its destructive (180 degrres out of phase) and antinodes when in phase.

That question is probs the difference between where I go to uni lol (and the 6 marker in section A)
Should I/someone create a new thread and we can collectively try and remember the questions and gain answers? Mainly just section A because it might get a bit messy with the others, anyone up for this?
Original post by HypErTwisT
Should I/someone create a new thread and we can collectively try and remember the questions and gain answers? Mainly just section A because it might get a bit messy with the others, anyone up for this?


Yes, do that please! :smile:


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I just wanna know astro question topics..cant remember what the questions were

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