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# OCR PHYSICS B G494~ 11th June 2015 AM ~ A2 Physics watch

1. (Original post by nair39)
For the logs question, I did, my answer was 3.86 * 10^-20.

Anyone get this, rather than 3.96? I've checked it again just now, so I'm sure it's right unless I made a silly mistake.

my answer was epsilon = ln10 / [(1/(300*k))-(1/(400*k))] which gives 3.86 * 10^-20
I think it was 2.something
I also think it was less than ln(10) too.
I got (ln(9.something) x k)/(1/300-1/400)

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2. (Original post by Mutleybm1996)
I think it was 2.something
I also think it was less than ln(10) too.
I got (ln(9.something) x k)/(1/300-1/400)

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definitely ln10 because it was just 10/1=e^...
3. For the question with the table about the SHM, I thought the x in the equation for the change in velocity was a multiplication sign and not x for displacement. I am so annoyed! Why couldn't they have used a curly x or put it at the start/end of the equation? I couldn't work out why my answers were wrong but I knew they were.
4. (Original post by bafid)
definitely ln10 because it was just 10/1=e^...
Oops I did 10-1
The rest was right though
How many marks lost?

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5. (Original post by Mutleybm1996)
Someone here did it using sim.equations and got 2.8 too

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Shame its wrong though, the answer is ln10*k/(1/300-1/400) type it into a calculator = 3.9*10^-20 - there is no other answer, youve made a calculation error somewhere
6. (Original post by bafid)
Shame its wrong though, the answer is ln10*k/(1/300-1/400) type it into a calculator = 3.9*10^-20 - there is no other answer, youve made a calculation error somewhere
If I did ln(10-1) but the rest correctly how many marks lost??

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7. (Original post by Mutleybm1996)
If I did ln(10-1) but the rest correctly how many marks lost??

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Probably only 1 because you've gone about it the right way
8. (Original post by Mutleybm1996)
If I did ln(10-1) but the rest correctly how many marks lost??

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1 if they dock you just the accuracy mark, but possibly 2 if they dock a working one as well for not dividing
9. (Original post by bafid)
1 if they dock you just the accuracy mark, but possibly 2 if they dock a working one as well for not dividing
How was that questions only worth two marks - there was so much work to do.
10. (Original post by Robbo54)
How was that questions only worth two marks - there was so much work to do.
Probably because it was that hard a lot of people may not of been able to do it. So if they can't they don't lose to many marks
11. I agree, normally that kind of question is worth 3 or 4 marks. I can imagine it'd be particularly difficult if you didn't do A-level Maths, although I'm guessing most people who do Physics do Maths too...

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12. This is what a friend and I think are acceptable answers, though there is some uncertainty in some of the longer explanation questions.

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13. g494.pdf (29.1 KB, 415 views)
14. (Original post by Robbo54)
How was that questions only worth two marks - there was so much work to do.
There is actually a quicker alternative way to work it out I think, I've done a similar question in a past paper.

G494 June 2012 Q11c)

And the mark scheme gave:

And yeah I forgot that method so I just done it the long way, using the additional space on the back.
15. Kinetic energy is transferred to elastic potential energy in the deformed satellite. But you probably get the mark for just saying kinetic energy is transferred to different forms of energy and then giving an example (heat or sound).
16. (Original post by Robbo54)
Ok for the natural log questions I divided the two values so you cancel the two constants, and re-arranged to get Epsilon, anyone do a similar method to this?
Yes
17. (Original post by nair39)
For the logs question, I did, my answer was 3.86 * 10^-20.

Anyone get this, rather than 3.96? I've checked it again just now, so I'm sure it's right unless I made a silly mistake.

my answer was epsilon = ln10 / [(1/(300*k))-(1/(400*k))] which gives 3.86 * 10^-20
i got 3.86 as well
18. For the one where you had to show that Tp = a constant if relationship was true, I said it wasnt true as they were all different (none were exactly the same). Will I be penalized for this?
19. (Original post by urz13)
For the one where you had to show that Tp = a constant if relationship was true, I said it wasnt true as they were all different (none were exactly the same). Will I be penalized for this?
Only a mark lost for your conclusion I reckon. As long as your calculations were right you'd get those marks.

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20. The last question is going to be a horror to mark because there are so many practical ways of doing it and every one can be done in either direction (i.e. pushing the frequency above 2Hz or below 0.2Hz.
21. (Original post by Greating)
This is what a friend and I think are acceptable answers, though there is some uncertainty in some of the longer explanation questions.

If those are right (which they seem to be) I've dropped between 7 and 10 marks I'd say, which is massively frustrating after averaging about 55/60 on past papers. Hopefully grade boundaries for an A* are around the 48 mark.

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