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AQA Physics PHYA4 - 20th June 2016 [Exam Discussion Thread]

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Original post by tophatmenis
What did people but as units for epsilon naught x Gravitational constant?


C?
Original post by Mango Milkshake
It doesn't decay at a constant rate. You can't just do 45/80.


Damn. I was initially doing it correctly too, but I decided to switch methods. How many marks was that? 3?
Original post by yellowfan1555
Damn. I was initially doing it correctly too, but I decided to switch methods. How many marks was that? 3?


yes it was 3 marks, don't worry about we've all messed up somewhere on this paper :smile:

for that question for future reference so you know, we had no values of what v inital was and no graph. we know that the voltage fell by 80% in 45s though. so as its exponential, we can simply say that the inital voltage was 1v and it fell by 80% to 0.2v

then its just a bit of rearranging into: 45s/ln(0.2/1) = around 20-25s something in that area is what i got
I don't think anyone does, but when someone gets a hold of the multiple choice, could they post it so we can get an unofficial markscheme of it? as i'd really like to know what i averaglely got on it to reassure me for section B, I was aiming for 18ish but some got me stuck between 2
Original post by Yo12345
What did people get for the gravitational potential at the centre of the 2 masses?


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-4GM/d?


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Original post by Yo12345


same, g.f.s would be 0 but potential is what you said, thank god i got that
Original post by Nathan2580
same, g.f.s would be 0 but potential is what you said, thank god i got that


I hope it is. Is it definitely correct?


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Vote if you haven't yet voted- http://www.thestudentroom.co.uk/showthread.php?t=4176850
Original post by Yo12345
I hope it is. Is it definitely correct?


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yep, look at this https://www.physicsforums.com/threads/gravitation-field-strength-potential-mid-point-between-two-equal-masses.507635/

its the same question as asked in our paper but a few years back, different answers to choose but the core question was to find the potential at the mid point between 2 masses, and the answer is -4pi bla bla bla, we got it right :smile:
I think it will be about 51 or 52 for an A. It's much harder to tell for A* and full ums though.
Answers to the MC here: http://www.thestudentroom.co.uk/showthread.php?t=4177478&p=65961084#post65961084
Original post by C0balt
NatSci, you? I applied to imp too


Maths
Original post by Nathan2580
yes it was 3 marks, don't worry about we've all messed up somewhere on this paper :smile:

for that question for future reference so you know, we had no values of what v inital was and no graph. we know that the voltage fell by 80% in 45s though. so as its exponential, we can simply say that the inital voltage was 1v and it fell by 80% to 0.2v

then its just a bit of rearranging into: 45s/ln(0.2/1) = around 20-25s something in that area is what i got


Thanks man :smile: Lol yeah i'll need to know that next year when i'm resitting haha
Original post by notanooblol
Maths

Cool, I could never do a maths degree haha
Would 59-62 be an A*?


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Original post by Yo12345
Would 59-62 be an A*?


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A* boundary should be 57/58 so yes
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ella97
Do you have to get a certain number of questions right on the multiple choice to get a good grade overall?
I can't help but think that this is gonna have 2014 level high gb lol
(edited 7 years ago)
Original post by ella97
Do you have to get a certain number of questions right on the multiple choice to get a good grade overall?


Nope, its total mark that counts
Original post by C0balt
I can't help but this that this is gonna have 2014 level high gb lol


Nah it will be lower, like 63/64/65 for 120 ums

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