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

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Reply 1380

Amirrryy

what did people get to 1B section a??? how did they do it

Reply 1381

vedderfan94

Original post by jph12

You are never supposed to use rounded figures in Maths or Physics in calculations... That's bad science/mathematics. The more rounded figures you use, the further from the true answers you get.

That is what every Maths and Physics teacher I have ever had have said to me: don't use rounded figures in calculations: always use the full answer you get in your calculator.

Yes, that would be true if they didn't give you the 1/400 in part (b). But the question was this:

3 (b) eli) The y ray detector detects 1 in 400 of the y photons incident on the facing surface of the
detector.
Calculate the activity of the source. State an appropriate unit.

So I think they want you to use only the 1/400. Otherwise there would be no point in giving you it.

Reply 1382

Harney94

when you had to read off the binding energy in the graph, what was the answer?

Reply 1383

vedderfan94

Original post by Jellybean732

They're not high? 58 in 2010 and 62 in 2011 for an A* - 90% was full UMS! Thought today's paper was pretty standard - nothing too hard except the intensity one.

They're higher than Unit 4. Unit 4 boundaries for two papers for A* were 56 and 58, compared to the two values you gave, and I find Unit 4 easier.

Reply 1384

iluvmaths

some one post the turning points paper

Reply 1385

jph12

I put 7.88, but you had to times it by the nucleon number. So, if it was 250, 7.88x250.

Reply 1386

charliebick

Original post by ZaffarM

Temperature for applied i got was 365k

This was posted from The Student Room's iPhone/iPad App

Yeah i think i got something like that, cant remember tho, what other answers did you get?

Reply 1387

DeftLeftHand

Original post by eryk

the paper was definitely harder then last year not to mention unit 4, grade boundries are definitelly gonna be lower thisx year . it's just the question how low the are gonna be :smile:

Rock bottom I hope :tongue:

Original post by skibur

Mate, I would be overjoyed if I was wrong, but for my section (Astro) it was arguably the easiest yet imo

I forgot that the grade boundaries were separate for each option, I did applied instead but that wasn't too hard either.... Its the main section that has me worried...

Reply 1388

Hulksmash

Original post by TheRenaissanceMan

Don't know what everyone was on I thought that exam was challenging

I don't know how the Physics Boundaries are so high

I don't think I'm going to get that A* anymore, never mind I only needed 70 ums in this to get an A overall.

Reply 1389

jph12

Original post by vedderfan94

The point in giving it would surely have been to give those who couldn't get the answer from bi) a chance to answer the second question, seeing as the question was reliant on getting bi) right.

Reply 1390

Onee-chan

Unofficial Mark Scheme:

1a) 17K
b) 15s
2a) 6 electrons
bi) Binding Energy:
- work done against strong nuclear force
- to separate nucleus into constituent protons and neutrons
bii) Messed this up! Correct answer should be:
7.86X206 = 1600Mev
ci) Two curves that add up to 3.0X10^22
ii) Basically N/N0 = 2/3
iii) 2.6X10^9 years
3a) cosmic rays and nuclear powerplants etc.
bi) area/ area of sphere
ii) Got this wrong as well! Correct answer should be:
400X0.62/3.7X10-3 (or 4X10-3) = 62000Bq
c) 0.26 counts s^-1
4ai) 0.256 mol
aii) 3.31 x 10^5 Pa to 3 s.f.
b) same distance travelled between collision
different crms/ KE
etc.
5a) I did a curve with decreasing gradient not sure if right.
bi) Just sub it into p = m/v where v = 4/3pi R^3
bii) 3.5x10^-15m
c) Too long so I'm just not gonna sorry! I think I wrote kQq/R^2 for the equation so probably messed it up anyway :c

It wasn't even "content" hard it was all these sly tricks! Hopefully I did okay. :c Though I'm already aware of 5 marks definitely lost...

Reply 1391

Aeyuin

Gonna lose my uni place by about 10UMS out of the possible 600. Nice :/

Think they'll allow it because it was so close?

Reply 1392

Amirrryy

Grade boundaries for section A and B turning points anyone??

Reply 1393

Amirrryy

Original post by Aeyuin

Gonna lose my uni place by about 10UMS out of the possible 600. Nice :/

OMG same! i think i am short by 11 UMS :'( gonna cry

Reply 1394

H2SO4

Original post by Notsocleverstudent

Btw for the 1st question, it's definitely 17K because the energy is given per second and 0.41 mass is not per second but 0.12 mass is per second...

The time taken for 0.12 kg to pass through is not 1second

Reply 1395

icedragon

Original post by jph12

The point in giving it would surely have been to give those who couldn't get the answer from bi) a chance to answer the second question, seeing as the question was reliant on getting bi) right.

Yeah exactly. The only time where you should use a calculated value rather than a given one is where they say "show that" in a previous question then you need to use that value later on. For example today one of the answers was 3.68 something and they said show it was about 4. Big error there.

Reply 1396

vedderfan94

Original post by Hulksmash

I don't think I'm going to get that A* anymore, never mind I only needed 70 ums in this to get an A overall.

Same, I need like 31 UMS for an A and I think I've probably just missed the A*, judging by the number of people saying it was straight-forward.

Reply 1397

Alex J

gosh all i want is an A so i can meet my offer. So much for that A* prediction xD

Reply 1398

QuangHa

My answers (I did Applied one)

Section A

1) 17K - 15s

2) a. n = 6
b. BE = Word has to be done to seperate a nucleus into its consituent nucleons (p and n)
BE = 1621 = 1600 (2 dp)
c. Graph drawn, atom of Pb = 3.0 - atom of U *10^22
2.6 * 10^9 for t
3) a. air/ground/blah blah
b. cross-sectional area of the tube/surface area of sphere = 3.86*10^-3 appr. 4*10^-3
c. A = 0.62 * 400 = 248 (rounded up to 250, dont think its a good idea...)
d. count rate = 0.26
4) a. 0.26 mol / 3.3*10^5 Pa
b. Similar = random motion/move with a range of speed
Diff = higher Crms in T=295K

5) a. graph y=m*X^1/3
b. 3.55-3.54 *10^-15 depends on method (you can use either density or r0)

Section B cant remember anything. It would help if anyone post anything on :biggrin: