OCR Physics B G495 Field and Particle Pictures June 21st 2011 Exam Thread

I'm sure I'll be fine, I've done well on the past papers I did.

How many did you do? What's your typical mark?

About 4 or 5, my typical mark is about 85-95%

Well done then , but try to do a few more 'til exam day. I have learned so much stuff (that we apparently need to know but is NEVER mentioned in ANY of the physic textbooks) by doing the past papers. How are you with section C?

could somebody please post a link to questions and answers on the article? i have one day to revise, really starting to panick now! also have a totally different exam tomorrow to be worried about! sheeeeeeeet, im off to bed! but yeah id really appreciate if somebody could do that, you can have all my +rep or whatever!!

maybe i'm being stupid, but i just can't figure it out. why on Q1c of the section c practice paper that has been posted does the '%uncertainty in t^2 = 2 x %uncertainty in t' ?!

when you square a value with an uncertainty, your uncertainty for the new value is doubled, it's just a rule of uncertainties.

I'm glad you posted that, I'd done a question where the answer hadn't needed to double the percentage uncertainty but I was sure I was right hahah! I'm pleased to see there's one thing I haven't forgotten! ^_^

For the specimen paper I don't get 9b, or at least where half the numbers the mark scheme are using come from...

And also 10.bii

Help anybody, please?

*shakes fist* OCR B! *shakes fist*

I found some discrepancies between the paper and the mark scheme when I did that question.

We know that: A = lambda x N, where lambda is the decay constant and N the number of nuclei.

To find N, the number of nuclei, we need to find the mass of the sample and divide that the mass of one nucleus, so N = mass of sample / mass of nucleus

To find the mass of the nucleus, use the atomic mass number of hafnium-178 (178) and the atomic mass unit (u), which is approximately equal to both the mass of one neutron or one neutron. Therefore, the mass of a nucleus = 178 x u = 3E-25kg

Subbing that back into N = mass of sample / mass of nucleus (where the mass of the sample is 5ng = 5E-9kg, NOT 5E-12kg as stated in the mark scheme, gives:

N = 5E-9 / 3E-25 = 1.7E16 NOT 1.7E13

Therefore, going back to A = lambda x N and subbing in the given value for lambda:

A = 7.1E-10 x 1.7E16 = 1.2E7

Thanks very much- I missed the bit about multiplying 178 by u!

And I think it is 1.7E13 because the mass is measured in ng not nkg!

Thanks again

http://www.school-portal.co.uk/GroupDownloadFile.asp?GroupId=642525&ResourceID=3903515

i just notice this link u guys post earlier.. is there any answer available for this?? help please.. just one day left for me. I am so worried

my teacher made them questions hahaha!

the official answers he put up are here:

http://www.skillspace.com/DIGITALLOCKER/Assets/View/155003bc-9a5a-4d4d-a233-7b48e4c8fbbd/0/Advance%20Notice%20Article%202011%20ANSWERS%20v2.pdf

I've just got like 64 for my past papers no ..! I need 80 to get in uni. God bless me!!
so regret that I didn't study much on this paper..
I would like to hv the mark sceme for feb11 paper, anyone got it??

http://www.school-portal.co.uk/GroupDownloadFile.asp?GroupId=642525&ResourceID=3903515

i just notice this link u guys post earlier.. is there any answer available for this?? help please.. just one day left for me. I am so worried