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# AQA Physics A - PHYA5 (18/06/12) - Exam thread Tweet

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1. Re: AQA Physics A - PHYA5 (18/06/12) - Exam thread
Hey . Wondering if anyone could help with a question. 'For a proton of Kinetic energy 5.0MeV show that its speed id 3.1x10^7ms^-1'

Now I figured I could just use eV=1/2mv^2 for this, therefore 5.0x10^6=1/2x(1.67x10^-27)xv^2
Therefore v=[(2x5.0x10^6)/(1.67x10^-27)]^1/2

This obviously doesn't give the correct answer. Is ev=1/2mv^2 not applicable here??

Thanks!

Just to add. I thought that the proton my experience relativistic issues as 3.1x10^7 is a little over 10% the speed of light. But they don't use relativity in the answer.
Last edited by timlewis101; 08-06-2012 at 20:31.
2. Re: AQA Physics A - PHYA5 (18/06/12) - Exam thread
Just did the specimen and it was quite hard! How did you guys find it compared to the June 11 paper?
3. Re: AQA Physics A - PHYA5 (18/06/12) - Exam thread
(Original post by timlewis101)
Hey . Wondering if anyone could help with a question. 'For a proton of Kinetic energy 5.0MeV show that its speed id 3.1x10^7ms^-1'

Now I figured I could just use eV=1/2mv^2 for this, therefore 5.0x10^6=1/2x(1.67x10^-27)xv^2
Therefore v=[(2x5.0x10^6)/(1.67x10^-27)]^1/2

This obviously doesn't give the correct answer. Is ev=1/2mv^2 not applicable here??

Thanks!

Just to add. I thought that the proton my experience relativistic issues as 3.1x10^7 is a little over 10% the speed of light. But they don't use relativity in the answer.
E = 0.5mv^2, where E is always in joules. So you have to convert the 5Mev to J by multiplying it by 10^6 and 1.6 x 10^-19. Then you should get the right answer.

Plus relativity must be ignored in the question or else the speed won't be more than c
4. Re: AQA Physics A - PHYA5 (18/06/12) - Exam thread
What papers are there available for this unit? Just June 10 and June 11? thnx
5. Re: AQA Physics A - PHYA5 (18/06/12) - Exam thread
(Original post by handsome7654)
E = 0.5mv^2, where E is always in joules. So you have to convert the 5Mev to J by multiplying it by 10^6 and 1.6 x 10^-19. Then you should get the right answer.

Plus relativity must be ignored in the question or else the speed won't be more than c
Thanks for the reply. In the case of an electron being accelerated through a p.d we can use the equation eV=1/2mv^2 , so surely the units for eV is the charge on an electron (e) times the accelerating voltage (V) thus meaning the units are eV. Its just annoying I cant get my head round why you can use eV=1/2mv^2 and at other times you have to use E=1/2mv^2
6. Re: AQA Physics A - PHYA5 (18/06/12) - Exam thread
(Original post by timlewis101)
Thanks for the reply. In the case of an electron being accelerated through a p.d we can use the equation eV=1/2mv^2 , so surely the units for eV is the charge on an electron (e) times the accelerating voltage (V) thus meaning the units are eV. Its just annoying I cant get my head round why you can use eV=1/2mv^2 and at other times you have to use E=1/2mv^2
you use eV when your dealing with voltages, and very high speed particles
7. Re: AQA Physics A - PHYA5 (18/06/12) - Exam thread
Need around 30 UMS in this exam to get the A for my offer so I'm not too worried, but I hope to get the A* overall. Astrophysics is the most difficult topic I reckon, hoping we get a nice 6 marker in each paper

I've still not started doing past papers :/
Last edited by vedderfan94; 09-06-2012 at 22:10.
8. Re: AQA Physics A - PHYA5 (18/06/12) - Exam thread
Also, if anyone's interested, below are the links (too big to attach on here) to some past paper question booklets that my teacher sent me. These are questions on each topic from pretty much all old spec papers I think. The vast majority are relevant to the current specification. Mark schemes and examiner's reports for all the questions are at the end of each booklet, so for those who have done all current spec papers these should keep you busy:

Astrophysics - http://www.4shared.com/office/cEKLrU...rophysics.html
Nuclear Power - http://www.4shared.com/office/Jt6GUJ...ear_Power.html
Thermal Physics - http://www.4shared.com/office/6cnLBK...l_Physics.html

Last edited by vedderfan94; 09-06-2012 at 22:36.
9. Re: AQA Physics A - PHYA5 (18/06/12) - Exam thread
(Original post by Onee-chan)
Just did the specimen and it was quite hard! How did you guys find it compared to the June 11 paper?
I found the Specimen Section A quite tough, the Applied Physics Specimen is relatively straight forward though.

As a rule specimen papers tend to be harder than actual papers I've found.
10. Re: AQA Physics A - PHYA5 (18/06/12) - Exam thread
Anyone got a link to the specimen paper? Cannot find it.
11. Re: AQA Physics A - PHYA5 (18/06/12) - Exam thread
(Original post by timlewis101)
Thanks for the reply. In the case of an electron being accelerated through a p.d we can use the equation eV=1/2mv^2 , so surely the units for eV is the charge on an electron (e) times the accelerating voltage (V) thus meaning the units are eV. Its just annoying I cant get my head round why you can use eV=1/2mv^2 and at other times you have to use E=1/2mv^2
I think the equation for kinetic energy that a particle with charge Q gains when it is accelerated through a p.d of V volts is QV. So we can equate QV = 0.5mv^2

the Q can be replaced with symbol e if its an electron as e = charge of electron which is 1.6 x 10^-19
So eV = 0.5mv^2 where it is e (charger on electron) * volts so it will be 1.6x 10^-19 times the volts.
12. Re: AQA Physics A - PHYA5 (18/06/12) - Exam thread
How do you derive one ideal gas equation from the other two:

If you know pressure is inversely proportional to volume then
and volume is proportional to temperature so
then you can sub into and you get
which says that pressure is inversely proportional to temperature but this is wrong as pressure is actually proportional to temperature.
What am I doing wrong?
13. Re: AQA Physics A - PHYA5 (18/06/12) - Exam thread
Nuclear and Medical Physics Notes from another post : http://www.thestudentroom.co.uk/show...4#post38026614

Good luck
14. Re: AQA Physics A - PHYA5 (18/06/12) - Exam thread
A lot of people doinig astrophysics, im doing turning points.

Havent covered it yet but Thermal/Nuclear physics seems quite nice, im guessing the optional topics is where the **** comes, and the synoptic parts. (Wave-particle duality, etc) but i havent done any papers, only questions so it may be very different when i do papers
15. Re: AQA Physics A - PHYA5 (18/06/12) - Exam thread
(Original post by beelz)
How do you derive one ideal gas equation from the other two:

If you know pressure is inversely proportional to volume then
and volume is proportional to temperature so
then you can sub into and you get
which says that pressure is inversely proportional to temperature but this is wrong as pressure is actually proportional to temperature.
What am I doing wrong?
We know:

Boyle's Law -
Charles' Law -
Pressure Law -

Multiply them all together

i.e
Last edited by desijut; 11-06-2012 at 17:22.
16. Re: AQA Physics A - PHYA5 (18/06/12) - Exam thread
What do you think the 6 mark questions will be on for Nuclear & Thermal and Astrophysics.
For Astrophysics, I think it may be on CCDs or stars in a binary system.
17. Re: AQA Physics A - PHYA5 (18/06/12) - Exam thread
(Original post by vedderfan94)
Also, if anyone's interested, below are the links (too big to attach on here) to some past paper question booklets that my teacher sent me. These are questions on each topic from pretty much all old spec papers I think. The vast majority are relevant to the current specification. Mark schemes and examiner's reports for all the questions are at the end of each booklet, so for those who have done all current spec papers these should keep you busy:

Astrophysics - http://www.4shared.com/office/cEKLrU...rophysics.html
Nuclear Power - http://www.4shared.com/office/Jt6GUJ...ear_Power.html
Thermal Physics - http://www.4shared.com/office/6cnLBK...l_Physics.html

18. Re: AQA Physics A - PHYA5 (18/06/12) - Exam thread
For turning points, do we have to know how Huygens explained refraction and reflection?
19. Re: AQA Physics A - PHYA5 (18/06/12) - Exam thread
(Original post by DonWorryJockIsHere)
For turning points, do we have to know how Huygens explained refraction and reflection?
I dont think so, i think we have to know that it explains refraction and reflection but not the nuts and bolts of it...
20. Re: AQA Physics A - PHYA5 (18/06/12) - Exam thread
Heyyy,
Been revising and I'm getting really muddled by special relativity in the Turning Points option. Like picking which one is t or t0 and l or l0. And which frame of reference you're in.
Just wondering if anyone could put it simply, or has any notes, that are less confusing that the textbook! :/
Any help would be reallyyy appreciated. Thanks.
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