PHYA5 ~ 20th June 2013 ~ A2 Physics

Also, what are people thinking for the six markers for the core/astro papers?

I'm personally hoping for thermal derivation of the pV=1/3NM(crms)^2, cause its mentioned on the spec.

For astro stellar evolution wouldn't be too bad, or comparing the advantages/disadvantages of refracting & reflecting telescopes. Not sure what else is a potential question really...

Help on June 12 part A 3)c) anyone? I'm stuck??

http://filestore.aqa.org.uk/subjects/AQA-PHYA5-1-QP-JUN12.PDF
http://filestore.aqa.org.uk/subjects/AQA-PHYA52A-W-MS-JUN12.PDF

It's not a sig fig question so you shouldn't worry too much, sometimes they'll even put the non rounded figure in brackets in the mark scheme like: 9.2 (9.15) but to be on the safe side just try to do the minimum sig figs in the question

paper was really easy to be honest. but i screwed. :/

I try to do this anyway but when I'm marking my own papers it gets a bit ambiguous Thanks!

Another similar thing is, when they say something like "Show x is about 5" so you show it equals to 4.9 and then in the next part you have to do a calculation with that number, do you use 5 or 4.9? My teacher said 4.9 but the mark schemes tend to use 5 :/

Use
C=k/x^2
find k from the original Count rate=0.62 and distance, the rest follows.

Is latent heat absorbed by the other mass? I'm guessing not but then what exactly happens to it?

Posted from TSR Mobile

What do you mean other mass ?

If something is being cooled down & the heat is going towards something else to reach thermal equilibrium then some of the heat given may be latent heat, that is if the cooling substance changes state ofcourse

Hey, on the June 2010 astro paper, q 2b ii) has stumped me.

It asks to calculate the difference in brightness of 2 stars (show that it's 8000)
the mark scheme says:
difference in magnitude = 9.8
so difference in brightness = 2.5^9.8

just want to know, where did this 2.5 come from?

Need help on 4c
Posted from TSR Mobile

A magnitude 1 star is 2.5x brighter than a mag 2 star. Each magnitude class is 2.5 times brighter than the previous one. So as there is a difference to 9.8 for the magnitude, the ratio of brightness is 2.5^9.8.

Hope that helps.

Okay so the question says 98 J are delivered each second.
So after 30 seconds, the total amount of energy applied to the ice is:
98x30= 2940 Joules.

We know that the temp change is 14 as it goes from -14 degrees to 0.

Then we can use the equation E = mc(delta)T and rearrange to find c, the specific heat capacity.
c = E/m(delta)T
so
c = 2940/ (0.1 x 14) = 2100 J kg^-1 K-1

the mass has to be in kg so convert 100g = 0.1kg
and the change in temp is the same whether Kelcvin or Celcius

*edit* I did the wrong question didn't I? ¬.¬
gahh, well, more practise for me I guess..

astrophysics related

can spherical aberration be completely eliminated by using parabolic mirrors?

I can't be certain, but I'm fairly certai you won't be getting a question on the gas law derivation directly. They do the six-marker tiered - you can't really tier a derivation, and it's too long to do as a "short" question.

Ah I see where you're coming from with the tier thing. Damn.

I can't really think what they could ask thermal side?

Unless its a nuclear question... although if it was something like discuss the principle features of a nuclear reactor which enable it to operate safely or something I wouldn't be fussed cause I find that pretty straightforward.