[PhysicsGirl]

(Original post by Dhanu123)
I got really confused then, I didn't know how I ended up on there :P
I have mixed opinions, I felt alright about G495, but maybe cause I really put my head down into it
G494 will be tricky... I sat it in Jan and it was a nightmare. hopefully it'll be much better this time
C3 is on Thursday, but I did a past paper to see where i was standing in terms of knowledge and I got 86%, so I don't need that much revision for that.. might as well start physics now.

I'm predicting wordy questions on gas laws... and temperature i think.
im really hoping for lots of calculation questions

This is my first sitting of G494- my college has us sit both physics exam in the summer.
Sounds like C3 is going well Good luck.

[Dhanu123]

(Original post by PhysicsGirl)
This is my first sitting of G494- my college has us sit both physics exam in the summer.
Sounds like C3 is going well Good luck.

same with us, but we asked to sit it in January... didn't got too well:P
thank you

[silvertear]

What is the definition of the Boltzmann factor?

My answer would be: The Boltzmann factor describes the proportion of particles that can reach the activation energy E.

Is that right?

[xiyangliu]

(Original post by silvertear)
What is the definition of the Boltzmann factor?

My answer would be: The Boltzmann factor describes the proportion of particles that can reach the activation energy E.

Is that right?

Yes. Which is also the probability of an event happening


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

[silvertear]

(Original post by xiyangliu)
Yes. Which is also the probability of an event happening


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

So maybe, The Boltzmann factor describes the proportion and thus the probability of particles reaching their activation energy E.

Would be slightly better?

[PhysicsGirl]

(Original post by silvertear)
So maybe, The Boltzmann factor describes the proportion and thus the probability of particles reaching their activation energy E.

Would be slightly better?

I think that sounds fine I've not seen any specific questions that ask for exact definitions in past papers, so I'm not entirely sure what the exact definition is according to a mark scheme, but I think it's more likely that you'll be tested on whether you can calculate it, and whether you can understand what it means (and hence apply it in your answers). It's also on the specification that you need to know what the graphs of it against temperature look like.

Mathematically, the B.F. gives you a value between zero and one (close to zero when the ratio epsilon/ kT is large, close to one when the ratio epsilon/ kT is small). That value is the fraction of particles that have the extra energy epsilon needed for something to happen, if that energy epsilon has to be acquired through random collisions with many particles at a temperature T.

Textbook definition : The Boltzmann factor, e^(-epsilon/kT) is the ratio of numbers particles in states differing by energy epsilon.

[EricEdwardSelvaraj]

I am so hoping this paper is straightforward. Some past papers are horrific like january this year.

[PhysicsGirl]

(Original post by EricEdwardSelvaraj)
I am so hoping this paper is straightforward. Some past papers are horrific like january this year.

Just out of curiosity, what makes you say that January was horrific?

[Amy-Rose]

Is impulse on this exam? Can't see any mention of it in my revision guide.

[PhysicsGirl]

(Original post by Amy-Rose)
Is impulse on this exam? Can't see any mention of it in my revision guide.

Yep, it's included in Chapter 11 of the textbook :-)

[Amy-Rose]

(Original post by PhysicsGirl)
Yep, it's included in Chapter 11 of the textbook :-)

Arghh its not in the CGP book! Anything else you think I may have missed?

[Oromis263]

(Original post by EricEdwardSelvaraj)
I am so hoping this paper is straightforward. Some past papers are horrific like january this year.

I'm not sure how it was in the exam hall, but I did it as a mock and found it quite nice? I think the only bit I really disliked was the part on Boltzmann. Well, hopefully that means Monday will be nice.

[PhysicsGirl]

(Original post by Amy-Rose)
Arghh its not in the CGP book! Anything else you think I may have missed?

I think it probably wasn't mentioned because since impulse is the force multiplied by the time for which it acts (this formula's given in your formula book), it's essentially a rearrangement of the idea that force is the rate of change of momentum, so it's not really an explicitly different principle (i.e. I think the CGP book will have covered the majority of the essentials, just not all of the finicky little details).
The CGP book is great, but because it is a revision guide, it simplifies the majority of the material in the course, hence it does miss out a few things. However, on the other hand, the textbook goes into overload, and more than covers the course, so you're kind of stuck between a rock and a hard place- we all are. You might have seen earlier on this thread I posted a revision checklist based on the specification, so if you're concerned about missing out on things, it might be worth taking a look at that, and broadly, if it's not on the specification (which can be found here: http://pdf.ocr.org.uk/download/kd/oc..._gce_spec.pdf?) , then it shouldn't come up in the exam, but this isn't as foolproof as you'd think, and at any rate, it's really rather difficult to know the specification precisely- it can be a bit vague in places!

[Oromis263]

(Original post by PhysicsGirl)
...

Did you see the finished mark scheme for C4? Here it is :P

[Amy-Rose]

(Original post by PhysicsGirl)
I think it probably wasn't mentioned because since impulse is the force multiplied by the time for which it acts (this formula's given in your formula book), it's essentially a rearrangement of the idea that force is the rate of change of momentum, so it's not really an explicitly different principle.
The CGP book is great, but because it is a revision guide, it doesn't fully cover the course. However, on the other hand, the textbook goes into overload, and more than covers the course, so you're kind of stuck between a rock and a hard place- we all are. You might have seen earlier on this thread I posted a revision checklist based on the specification, so if you're concerned about missing out on things, it might be worth taking a look at that, and broadly, if it's not on the specification (which can be found here: http://pdf.ocr.org.uk/download/kd/oc..._gce_spec.pdf?) , then it shouldn't come up in the exam, but this isn't as foolproof as you'd think, and at any rate, it's really rather difficult to know the specification precisely- it can be a bit vague in places!

Yes I had a look at the checklist and it was really helpful! Thank you. What I've decided to do is just go through the text book for its key points and check I have them already or if not, revise over them too. Thanks.

[EricEdwardSelvaraj]

(Original post by PhysicsGirl)
Just out of curiosity, what makes you say that January was horrific?

They seem to put the questions in quirky contexts like that pulse and aircraft question. And in June 2011, they seem to use a lot of different models and formulae within the question. It takes me forever to even understand the question.

[PhysicsGirl]

(Original post by Amy-Rose)
Yes I had a look at the checklist and it was really helpful! Thank you. What I've decided to do is just go through the text book for its key points and check I have them already or if not, revise over them too. Thanks.

No worries! I'm glad I could help. Just out of curiosity, are you sitting G494 for the first time, or is it a resit? A friend and I were arguing over whether or not it's common for colleges make candidates sit both of the exams in the summer

[PhysicsGirl]

(Original post by EricEdwardSelvaraj)
They seem to put the questions in quirky contexts like that pulse and aircraft question. And in June 2011, they seem to use a lot of different models and formulae within the question. It takes me forever to even understand the question.

Do you mean the question about worldlines? I'm just thinking that it might be a good idea to go through the questions that people found particularly difficult in past papers.
And yeah, I agree that understanding what the question is actually asking is half the battle; that's really the reason I try and do as many past papers as possible- it's much more about improving your exam technique than it is improving your knowledge/ understanding of topics.

[Amy-Rose]

(Original post by PhysicsGirl)
No worries! I'm glad I could help. Just out of curiosity, are you sitting G494 for the first time, or is it a resit? A friend and I were arguing over whether or not it's common for colleges make candidates sit both of the exams in the summer

A resit for me, lack of revision over christmas and a mini-panic on a couple of questions!

[Oromis263]

(Original post by PhysicsGirl)
No worries! I'm glad I could help. Just out of curiosity, are you sitting G494 for the first time, or is it a resit? A friend and I were arguing over whether or not it's common for colleges make candidates sit both of the exams in the summer

I would say it's not common...