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

Cool! And is it >1.4 solar masses = neutron star, >3 solar masses = black hole?


Posted from TSR Mobile

Sounds right off the top of my head (after tomorrow, physics and chemistry revision restarts for me!)

Yeah I've been slacking recently. As you can probably tell. Last day of college was today so I'm now officially free!


Posted from TSR Mobile

Same! (on both the slacking and the end of term between maths exams and it being the last few days I just haven't done anything much). Did you do anything for the end of term?

Nice! Sounds like a good thing - gotta have a break to make sure you don't have a breakdown haha!

Not exactly yet! Our college leaver's ball isn't until late June so celebrations don't quite start yet yourself?


Posted from TSR Mobile

True, just hoping I don't struggle too much to get back into things now!

Ah we don't have a leavers ball or anything fortunately (they got the hint after they tried a Christmas ball last year and lost loads of money on the venue because literally no one went), just had leavers afternoon today which involved a bouncy castle and a bungee run (tbh just made me think about M2 way too much) in the town park conveniently behind college and some people got exceptionally drunk for that time of the afternoon. Also a bunch of people bought foam swords and water pistols so that was fun

That sounds the oddest (yet still undeniably cool) way to end 2 years :L

Leaver's ball is a Las Vegas theme this year. They've hired a hall, a DJ and there will be poker tables, a bar for over 18s and fireworks - sounds more spectacular than it will probably turn out tbf Hahahah.


Posted from TSR Mobile

What about this?




Posted from TSR Mobile

Yeah our college has finally accepted that we're all five year olds at heart at one point a guy from my maths & physics classes had a foam sword to my neck and was shouting "don't move or I'll kill the princess" (I'm the most cheerful looking hostage you've ever seen in the photos ).

Sounds like it could be fun, although not really my thing (I regretted going to year 11 prom)! We've also got a night for over 18s to go get plastered at one of the local... clubs? Night out places? I don't know what to call it, I don't drink but I don't think I'm going to that.

I reckon the life cycle of stars is gonna be the 6 marker, well there certainly wasn't a great deal on the life cycle of stars on the 2014 paper anyway.

Had a question, does anyone know how much of the derivation we need to know for the kinetic theory gas equation?

Thanks - this is great!

Posted from TSR Mobile

No problem! How would you go about answering a six marker on the life cycle of a star?


Posted from TSR Mobile

Do you think they would ask about the life cyle of stars generally or for a more specific mass one?

Probably a two star (X and Y) one where X has a larger mass (>3 solar masses) and Y has a lower mass (~1.4 solar masses).

Would you describe the following being the same for both:
Planetary nebula
Protostar
Main sequence

Then the path splits?

What confuses me is that I thought:
• larger stars go on to form a red giant, red super giant, supernova then form a black hole or a neutron star?
• smaller stars go onto being a red giant, then a white dwarf, then cool to become a black dwarf?

But, if a type Ia supernova is formed from a white dwarf, how does that alter the life cycle? Because surely a white dwarf can then result in a neutron star or black hole?


Posted from TSR Mobile

Yeah you would describe the initial stages together and then split.

Not that I know of, the white dwarf still doesn't have enough mass to form a neutron star or a black hole I think? Because those aren't side effects of the supernova, they happen because outward pressure from fusion stops and there's just too much mass.

I see, sorry. I didn't really understand it in class. So a white dwarf generally just cools to a black dwarf but can cause a supernova in a binary system with a main sequence star?


Posted from TSR Mobile

Yes, if the conditions are right in the binary system If we're asked about the life cycle of a star though you wouldn't talk about type 1a supernova, just the standard life cycle.

Thanks for clearing that up - I would have otherwise struggled to get 3/6 marks haha!

In terms of "hydrogen burning" - is this the only stage of fusion we need to describe? Or do we need to know further stages?


Posted from TSR Mobile

I'd imagine we talk about the fusion of helium into heavier elements for the red giant stage. I really need to revise the life cycle of a star properly because I am pretty sure it's going to come up, after doing the 2013 and 2014 paper neither of them had a question about the life cycle of stars. All there was was the question about 1a supernovae