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

1. (Original post by lefneosan)
So why do graphs such as the following:http://hyperphysics.phy-astr.gsu.edu...nucbin.html#c2 say trhat ements heavier than iron can yield energy by fission?
Fission is the splitting of a large nuclie into two. So as a large nuclie breaks down the products will have a larger nuclear binding energy per nucleon, hense it will be shifter more to the left.
In any reaction where the nuclear binding energy per nucleon increases energy is released. (Which is a good thing!)

e.g. look at the modified graph ive attached. The blue element thats heavier than iron can break down into the two smaller ones that have a larger nuclear binding energy per nucleon, hense yield energy.
Attached Images

2. (Original post by Bulmer)
Just a quick question with something i always get confused about..

When answering calculation questions, what significant figure / decimal place should you leave you answer at??

Thanks.
In exam questions there isn't any point in quoting your answer to a greater accuracy than provided in the question. So if the question gives the data to 3 significant figures, always give your answer to 3 significant figures as well. Same is true for other numbers of significant figures, though you probably won't penalised if you write your answer to 1 significant figure greater, just don't write all the digits on your calculator!
3. (Original post by Uberuvy)
Fission is the splitting of a large nuclie into two. So as a large nuclie breaks down the products will have a larger nuclear binding energy per nucleon, hense it will be shifter more to the left.
In any reaction where the nuclear binding energy per nucleon increases energy is released. (Which is a good thing!)

e.g. look at the modified graph ive attached. The blue element thats heavier than iron can break down into the two smaller ones that have a larger nuclear binding energy per nucleon, hense yield energy.
great stuff thanks
4. "The student decides that if there really is no atmosphere above the height of 100km this velocity must be equal to the escape velocity. The escape velocity is the minimum velocity needed for any particle to escape from the Earth's gravitional attraction. He obtains an expression for the escape velocity, starting with the total energy of a molecule at this height, i.e KE + P.E "

why do you assume total energy is zero?
5. When comparing gravitational and electric fields is it enough to state the equations for each which are similar? The book doesn't give any explanations of the similarities, just a table of the equations...
6. (Original post by Kameo)
"The student decides that if there really is no atmosphere above the height of 100km this velocity must be equal to the escape velocity. The escape velocity is the minimum velocity needed for any particle to escape from the Earth's gravitional attraction. He obtains an expression for the escape velocity, starting with the total energy of a molecule at this height, i.e KE + P.E "

why do you assume total energy is zero?
Because he wants to get a minimum velocity needed, so that the energy after it escapes is at minimum (i.e. 0).
7. i thought i will go through each and every page of this thread, but its a seemingly impossible task. so here i come straight-off to page 18.

hope i havent missed anything important. (i know i have)

i have chem5 on monday morning so i have to divide my time beteewn the two

phy5 seems ok. astrophysics is a BIG problem
8. (Original post by kosy91)
i thought i will go through each and every page of this thread, but its a seemingly impossible task. so here i come straight-off to page 18.

hope i havent missed anything important. (i know i have)

i have chem5 on monday morning so i have to divide my time beteewn the two

phy5 seems ok. astrophysics is a BIG problem
Slightly off topic, but did you firm Nottingham?
9. (Original post by JayAyy)
Slightly off topic, but did you firm Nottingham?
oh yes I did....for engneering though, at UP campus. a classmate of mine from kenya has firmed nottingham for economics

to get back on topic, hows build-up for the physics exam?
10. (Original post by kosy91)
oh yes I did....for engneering though, at UP campus. a classmate of mine from kenya has firmed nottingham for economics

to get back on topic, hows build-up for the physics exam?
Ahh ok. Might see you there (Afro-Caribbean society )

Not going well, haven't touched Unit 5 in ages because of my other exams
How's yours going?
11. (Original post by JayAyy)
Ahh ok. Might see you there (Afro-Caribbean society )

Not going well, haven't touched Unit 5 in ages because of my other exams
How's yours going?
is that scoiety for citizens of african nations or people of african descent? because i am a kenyan but indian descent!!

i had 4 maths modules over a gap of two days each so i couldnt really revise for physics. the worst part is, i know i have done badly in unit 6(intl. alternative) so i need to put in a big effort in unit5....oh well...
12. (Original post by kosy91)
is that scoiety for citizens of african nations or people of african descent? because i am a kenyan but indian descent!!

i had 4 maths modules over a gap of two days each so i couldnt really revise for physics. the worst part is, i know i have done badly in unit 6(intl. alternative) so i need to put in a big effort in unit5....oh well...
Ohhh, I assumed you were black because your flag was Kenyan. Sorry

Damn, that's alot. Well, we have the weekend and a day to fully focus on Unit 5 now. Let's make the most of it
13. Are there some things in the Edexcel book that we don't need?
Because there are small sections which don't appear to be on the spec but are in the book..unless they are included under a general heading on the spec.
E.g. the bit about Change of state on page 109.
14. (Original post by kathx1)
Are there some things in the Edexcel book that we don't need?
Because there are small sections which don't appear to be on the spec but are in the book..unless they are included under a general heading on the spec.
E.g. the bit about Change of state on page 109.
the spec is vey vague in my opinion. its best to stick to edexcel endorsed books, and refer to the spec from time to time

which book is this page from? the miles hudson one?
15. (Original post by kosy91)
the spec is vey vague in my opinion. its best to stick to edexcel endorsed books, and refer to the spec from time to time

which book is this page from? the miles hudson one?
Ah should have said which book haha.
It's Edexcel Physics for A2, Hodder Education.
By Tim Akrill and Graham George.
16. (Original post by kosy91)
the spec is vey vague in my opinion. its best to stick to edexcel endorsed books, and refer to the spec from time to time

which book is this page from? the miles hudson one?
Nah, that's from Hodder book, that's endorsed by Edexcel anyway.
We dont need to know particulary about plasma, as it's not in the syllabus.
I guess they just put it there for understanding of absolute zero.
17. (Original post by kathx1)
Ah should have said which book haha.
It's Edexcel Physics for A2, Hodder Education.
By Tim Akrill and Graham George.
(Original post by yadas)
Nah, that's from Hodder book, that's endorsed by Edexcel anyway.
We dont need to know particulary about plasma, as it's not in the syllabus.
I guess they just put it there for understanding of absolute zero.
oh alright. IMO that is complete nonsense. i dont see what you can get by reading that page.

talking about spec content.....is latent heat of fusion/vaporisation (kinetic theory section) and gravitational potentials in our syllabus??!! the hodder book seems to have covered it
18. (Original post by kosy91)
oh alright. IMO that is complete nonsense. i dont see what you can get by reading that page.

talking about spec content.....is latent heat of fusion/vaporisation (kinetic theory section) and gravitational potentials in our syllabus??!! the hodder book seems to have covered it
I don't think we need it....I don't remember ever covering it in class. Don't hold me to that though lol.
19. ok everyone, good night.
20. Goodmorning Have to do a thorough phy5 revision today
and I have to start on the questions too.

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