Over 50 in all I've done bar 2014, I think something like 47 for that one. This paper however I was not expecting to be so abstract, so it took a while for me to find my concentration. The binary star question was the main culprit. Wbu?

Reply 64

Jm098

Original post by TheFarmerLad

Yeah haha sounds like you're in exactly the same boat as me! That question was bad but I made too many silly errors e.g. that KE/EPE graph

Reply 65

TheFarmerLad

Original post by Jm098

Yeah haha sounds like you're in exactly the same boat as me! That question was bad but I made too many silly errors e.g. that KE/EPE graph

Ah I made other errors two mate. Hopefully the grade boundaries are kind!

Reply 66

tochicool

Original post by teachercol

5/4pi difference is same as 3/4pi difference so should get the mark.

Thank you sir!

Reply 67

ComputerMaths97

Got anywhere from 45-51 based on ecf. Happy with that, reckon I have a decent chance of an A*, and if not at least close I hope.

Reply 68

TheFarmerLad

@teachercol For the binary star question, could you treat the centre of the two circular motions to be a body of mass (M1 + M2 all divided by two) as the question said the two stars orbit about their centre of masses. By doing this could one then say : (v1)^2/R1 = (G)(M1+M2/all divided by two)/ (R1)^2 or (V2)^2/R2 = G(M1+M2/all divided by two)/ (R2)^2? If unclear I'll attach a diagram

Reply 69

Skylarkman

Desperate for an accurate prediction of the grade boundaries

Reply 70

username1969391

Original post by Skylarkman

Desperate for an accurate prediction of the grade boundaries

I think it will be similar to last years...

FULL 51
A* 47
A 43
B 39
C 35

Then again, that's probably me being a bit too hopeful. A lot of people seemed to find it much easier than I did

Reply 71

lai812matthew

binary system is in the spec? :s-smilie:

Reply 72

HarshaPeed

I think I completely misinterpreted Question 1. Didn't it say why these lines have the same gradient?
I said they were parallel lol and have the same change in y/change in x ratio. And for the triangles being a different area i just said they had different bases and perpendicular height so when you applied the formula for area of a triangle you would get a different area. oh my lord.

Reply 73

Spectral

@teachercol

Going back to q5e, it seems you forgot that the eqn for Fgrav in binary star systems is F=GM1M2/(R1+R2)^2, because you went back and equated F=mv^2/R to F=GM1M2/R1^2 (forgetting one of the radii) hence getting the wrong result

Reply 74

penguinsarefunny

I agree with you that the answer is wrong so worked through it again properly to check it. Do you agree with this answer?

Reply 75

jazzypeas

Difficulty poll:
http://www.thestudentroom.co.uk/showthread.php?t=4176590&p=65956530#post65956530

For grade boundary estimates :smile:

Reply 76

botnatsume

Original post by Kevinwong

You're wrong about the planets the answer is 1x10^33

Posted from TSR Mobile

yeah, that answer gives me a chill
i got E^33 too
hope he is wrong

Reply 77

Danny.L

Ignore the number in the brackets, thats me tallying how many marks i dropped worst case.
If anyone could help put my mind at ease for some of these that'd be great.
2)
c)ii)
R = mg + Fsin55 = 92 x 9.81 + (8.25 x 25)sin 55
= 902.5+169 = 1071N (3)
I omitted the Multiple by 25 by 8.25 and instead did Weight plus 8.25sin55.
Is this likely to get 1 or 2 marks out of the 3? (-2/3)

Q3 a)iii)
Left in Pi :/
b) i) I just flipped the EPE curve, is that both marks out the window?
ii)&iii) I then calculated these using 80mJ opposed to 50, would I drop all of these marks, or would I get e.c.f? (-3/5)

Q5e) Used keplers third law and got 1.73*10^33 :/
Is that 3 marks out the window? Or could I (hopefully) get 2 for this method? (-2/3)

Q6)a) Possibly didnt answer in enough detail. (-1/2)
d) So stupid, was rushing at this point, stated 2x the energy input, but not 2x mass so said temperature would increase by 2. Ridiculously stupid. Would I get 1 mark for stating that energy input is doubled, or is it 1 mark for saying constant and 1 mark for correct explanation? (-2/2)

Q7)a) Not enough detail (-1/2)

Worst case 49/60. Very disappointed considering I was getting 58+/60 on my past papers. Absolutely kicking myself.