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# AQA Physics PHYA5 - Thursday 18th June 2015 [Exam Discussion Thread] watch

1. (Original post by Adangu)
I know hardly anyone does it! Thank you so much for writing out the list! I think it is probably going to be on engines too. Or maybe fridges and heat engines?
Yeah haha ikr! No problem mate, i hope it wont be on fridges/reversed heat engines etc, not much you can say about it. Although thought just came to me that we're not supposed to know the cycles for fridges or reversed heat engines, maybe we're asked to describe it or something?? How are you finding calculations?
2. (Original post by MrKlaus)
Do we need to remember all the stuff about the stages of hydrogen burning & all that?
I'd just look to say the star converts hydrogen to helium through fusion during its main sequence stage. Once the hydrogen runs out it becomes a red giant
3. (Original post by betbi3etwerrd)
What are some points on the stability curve (Z against N) that remembering them will help.
Remember the number 80. Then just times it by 1.5 to get 120 as the curve passes this point. And initally starts off similar to n=z with these to points you can draw a pretty accurate curve
4. (Original post by Mehrdad jafari)
But do they not have the same mass as the electrons?

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Positron is the antiparticle of an electron, which means they have the same mass.
5. I reckon the 6 marker will be on how a Pulsar's strong radio source affects the environment of Earth.
6. (Original post by Mehrdad jafari)
But do they not have the same mass as the electrons?

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Yes, the same argument applies, from my knowledge you don't have to include them due to their insignificant mass
7. (Original post by ricardomontoya97)
I reckon the 6 marker will be on how a Pulsar's strong radio source affects the environment of Earth.
This would never get asked
8. (Original post by a.a.k)
forhalf life definition its not the mass that halves its the number of radioactive atoms that halve.
Which technically is the same, since the mass is proportional to the number of atoms of the particular isotope
9. Please help ME on part b iii thanks and the mark scheme has a formula s=Theta x r where did that come from?
10. (Original post by Mehrdad jafari)
Would anybody be kind enough to tell me why in june 13 paper the mark scheme doesn't take account of the mass of the positrons?
Attachment 431289

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I've also just done this past paper and it does take into account the mass of the positrons

E = (4 x 1.00728u) - (4.00150u + 2 x 5.5x10^-4 u) = 0.02652u
E = 0.02652u x 931.5 = 24.7 MeV
11. (Original post by Mehrdad jafari)
But do they not have the same mass as the electrons?

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Sorry it seems i was wrong. You do take into account the positron
12. (Original post by palaseum9)
Positron is the antiparticle of an electron, which means they have the same mass.

(Original post by SuperMushroom)
Yes, the same argument applies, from my knowledge you don't have to include them due to their insignificant mass
Thank you both of you. Im just confused that they took account of the mass of the electrons but not positrons. Anyway, i don't even want to think about it now, i think it's too late

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13. (Original post by essl96)
I've also just done this past paper and it does take into account the mass of the positrons

E = (4 x 1.00728u) - (4.00150u + 2 x 5.5x10^-4 u) = 0.02652u
E = 0.02652u x 931.5 = 24.7 MeV
Thanks. Why 2*5.5*10^-4 and not 4*5.5*10^-4 since there are 2e and 2 positrons?

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14. Just remember guys, before you write anything ask yourself, 'would an idiot put this'. And if that answer is no do not write down that thing.
15. (Original post by Mehrdad jafari)
Thank you both of you. Im just confused that they took account of the mass of the electrons but not positrons. Anyway, i don't even want to think about it now, i think it's too late

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I think you may have accidentally included the electron neutrino in your answer? You seemed to have multiplied the mass of an electron (5.5x10^-4 u) by 4 when it should only be multiplied by 2. The mass of a neutrino is nothing so you don't need to include the 2 neutrinos in your answer!
16. (Original post by palaseum9)
SHC/Specific latent heat experiment may pop up, but the one we think is most likely to come up is the derivation of p=1/3Nmc^2 equation, but you know what AQA are like...

For turning points, the Michelson-Morley experiment perhaps??
thats what i thought!!!1 although im also thinking, since its a rewrite, they may just give us next years paper, so probably not what we think
17. (Original post by RemainSilent)
so there is a chance that the papers MIGHT be easier?
No. We can never presume anything. There are two ways AQA could have thought:
1: Damn! Our papers were stolen again, better whip up a paper at the last minute and make it ridiculous because we're so so angry
2: Quick! Write a paper at the last minute, who cares what goes into it! Which would be the slightly easier outcome. But probably full of mistakes

But basically, we have no idea what it'll be like.
Although if it means anything, I know some people who did the BIO5 exam today that was a re-write and apparently it was horrible.
18. (Original post by SuperMushroom)
This would never get asked
I think it will. There's quite alot to say about it really.
19. (Original post by Ilovemaths96)
Yeah haha ikr! No problem mate, i hope it wont be on fridges/reversed heat engines etc, not much you can say about it. Although thought just came to me that we're not supposed to know the cycles for fridges or reversed heat engines, maybe we're asked to describe it or something?? How are you finding calculations?
Yeah it'll probably be on engines or momentum then. It's just I know AQA like :L

Honestly calculations are hard, easy to miss conversions. Although some questions are just look at the formula booklet, some of them really mess you about. I'd say applied physics is quite hard indeed

How you finding it?
20. (Original post by essl96)
I think you may have accidentally included the electron neutrino in your answer? You seemed to have multiplied the mass of an electron (5.5x10^-4 u) by 4 when it should only be multiplied by 2. The mass of a neutrino is nothing so you don't need to include the 2 neutrinos in your answer!
Damn, i thought neutrinos were the same as electrons. I did OCR last year and so we didn't do particle physics

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