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Edexcel A2 Physics Unit 5 'Physics from Creation to Collapse'

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Mrcarrot

The white dwarf/red giant questions was quite confusing i thought? the two realistic choices were, iirc: 1) red giants are larger and cooler than our sun or 2) white dwarfs are smaller and hotter, right? if someone can remember exactly, then that might explain my (potential) mistake, as i said that red giants are larger and cooler than our sun. but otherwise, surely both of those are correct..

That's what I thought so I was confused...I thought both were correct surely. I ticked it being the red giant being cooler and larger, because I thought that technically since white dwarfs cool down maybe not all of them are hotter than the sun. Why was the white dwarf one correct?

Reply 1061

skannan.91

bradley.sparkes

Who else feels cheated by the first SHM question? I swear to god it specifically stated that the mouse was on a floor where hardly any frictional forces worked on the mouse and even the picture showed a mouse on a horizontal plane. That question completely threw me because of this, otherwise I would have used the T=2Л√M/k and possibly got the full 5 marks :frown:

i got cheated in the picture it looked like it was on the floor and it said frictionless horizontal surface

Reply 1062

yadas

I think they said just giants, not specifically red ones.
And the blue ones have higher temperature than the Sun.
Dwarfs (that are not on the main sequence) all have higher temperature and are all smaller than the Sun.

With the mouse question, got confused too.
Answered it at the end, when I realised I have enough time to read it again.
They said it was placed horisontally, and in equilibrium it was extended by 20cm.
From this we can find the spring constant, and find the time (hence the frequency) of the oscillations.

This paper is about to be the most discussed if you guys continue posting with the same speed. :biggrin:

I personally didnt read all the replies.. :K:

Feel sorry for Doughboy.. =\

Reply 1063

skannan.91

in MCQ for the HR diagram it is white dwarf is smaller and hotter than sun because the other 2 options just said giant stars, nothing specific e.g. red giants, super giants.

for the question about how radio acticvity can be detected, i put that electron can travel through your body and Am emits electron, it can be detected using electric field.

for the fraction part i got 1/8

so for the activity, i just divided the initial activity by 8, as the initial amount would have decreased by a 1/8 in 24 hrs.

for the parallax question, i put the measurements are used to calculate distance and it is used to calculate the angle the star moves through,

for the diagram i drew the one in the book but i am not sure if I put all the labels on.

for another method i put standard candles can be used.

for the question about the lungs, the assumption i put was N(number of molecules) and temperature was constant, but now i think its N is constant and air is an ideal gas, looking at the revision guide there is an equation for fixed mass which can be use to calculate new T,P or V and that says 3 of them can change.

the rate of energy transfer i got 2.2W.

for the question about nuclear fusion, i got 5.6 MeV.

for the conditions needed for fusion, i put high temp. and density to overcome repulsive force of the +vely charged nuclei.

there was a question about circular motion, it was mainly show that question and asked you to work out the mass of earth i got something like 5.998.., so i put 6.0*10^24 Kg.

for the question where it asked about redshift and the inferences made by hubble, i quoted the formula for Z, and said its a measure of spread of frequency and hubble found out large redshifts mean the objects are far away from us and moving away from us.

the song part was annoying, i got hubble constant to be 2.34*10^-18

for the question about why we can never get a true value for the age of universe, i quoted the lines in the song and basically said universe formed a very long time so evidence is not available.

For the last question the first part was easy i wrote resonance and when driving freq.=natural freq.

for the velocity calculation i got something like 0.18ms-1

you also had to mark points on the graph,

x-when displacement is max., so it should be when velocity is 0.
y-when acceleration is 0, so that should be when velocity is maximum.

the last part was so annoying-tuned mass dampers.

i said that damper will also oscillate at the resonant frequency when the bridge does so, because it is tuned to that frequency, and energy from the oscillations of the bridge will be transferred to the damper, the damper then dissipates the energy.

Reply 1064

Jonzky

I do have the paper(s) (Unit 4 + 5). 5 Has been scanned already and should be up very soon.
Overall I thought it was a hard paper but I battled my way through it.

Reply 1065

Doughboy

Fraction is NOT 1/8. It's 7/8.

Question asked for what was decayed. 1/8 was what's left so 7/8 must've decayed.

Reply 1066

Doughboy

yadas

I personally didnt read all the replies.. :K:

Feel sorry for Doughboy.. =\

I had it coming anyway :rolleyes:

I just need to see the 6PH04+5 papers and deduce how many marks I got. I'm pretty sure my As in Biology, Chemistry and Maths are confirmed. A* in Chemistry most likely. A* in Maths or Biology MIGHT be possible depending on boundaries.

I'd be really happy with A*AAA. Just need to scrape it in Physics.

Reply 1067

Doughboy

unamed

yes, it is indeed the star dance.

[I assume you meant distance, which it is]

:woo:

no more exams!

LMAO

Yea, I meant distance. What an embarrassing typo!

Reply 1068

Pegasus92

Doughboy

I had it coming anyway :rolleyes:

Dnt worry youll get more than that.

Reply 1069

Doughboy

Pegasus92

Dnt worry youll get more than that.

All those cliche cheer-ya-up lines don't work on me :p:

How'd you think you think overall for all your subjects?

Reply 1070

Pegasus92

Doughboy

All those cliche cheer-ya-up lines don't work on me :p:

How'd you think you think overall for all your subjects?

I did shape.

Reply 1071

Pegasus92

Jonzky

I do have the paper(s) (Unit 4 + 5). 5 Has been scanned already and should be up very soon.
Overall I thought it was a hard paper but I battled my way through it.

Are you posting it today?

Reply 1072

omegaSQU4RED

For the question about assumptions of the air in the person's lungs, would it be correct to say that the mass and temperature of the lungs would have to remain constant?

Reply 1073

Pegasus92

OL1V3R

For the question about assumptions of the air in the person's lungs, would it be correct to say that the mass and temperature of the lungs would have to remain constant?

yeah it is correct.

Reply 1074

unamed

bradley.sparkes

Good priorities right there :wink:

Well, after these exams, I've developed a certain dislike for examboards, so I couldn't quite resist! :p:

PinkGothicLady

Interestingly my Physics teacher pointed out this mistake to us a couple weeks ago.. and sent an e-mail to Edexcel pointing it out. He never got a reply but perhaps they did read his e-mail after all and that's why they changed it. It would have panicked me a bit if it wasn't for the fact I recognised what they'd changed as our teacher had had us all check it a couple weeks back..
It really wasn't necessary for them to change that for this exam as I imagine it only panicked people. It always makes me uneasy when you get an exam paper with amendments in it. It puts my guard up as to what else might be wrong in it.

I really wasn't that worried, since they said it was something to do with the formula sheet. I'm always wary with exams.. :smile:

Doughboy

LMAO

Yea, I meant distance. What an embarrassing typo!

Nah, it made me laugh when I looked at it! :biggrin:

Reply 1075

kosy91

hey guys, that question about Anaught went something like this

the activity is 1.5MBq. sample prepared 24hrs before . find initial activity

A=1.5

lambda=ln2/8

t=1( 24hours=1day)

so when you find Anaught, you get and answer of 1.6........MBq

Reply 1076

kosy91

fredbraty

kosyyyyyyyyyyyyyyyyyyyyyy,where are you man????????
How did you do?
I hope you did well :smile:

heyyyyyyyyyyy

i have been sooo busy fater the exams. i went to school today, first thing in the morning, and gave back ALL the text-books i had. i mean, my room was literally full of them!!!

i have gone through your posts, and i agree with oyur take on this exam. this paper LOOKED easy. but in essence it was NOT. it had a lot of tricks tbh...and there was soo much explanantion.

i think i did ok-ish. well yes, i have dropped too many marks in MCQ and explanations

lets see what happens. I really want a very strong UMS in this to cover up my lack-lustre performance in Unit6 (intl. alternative)

cheers

Reply 1077

dimi3

JayAyy

I can't believe a scientist actually got emotional and argued about the lyrics in the song :facepalm2:

lol, i read somewhere that this scientist got a hissy fit over mariah carey's album E=MC2 and the he was all like "you're misguiding people blah blah blah..."
i dont know what happened after that :dontknow: