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    Not seen a thread for this, and I'm yet to find anyone else doing it. I'm hoping there is at least one other person! How are you finding past papers?

    Also, to anyone who has already done DE, any tips?
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    DE doesn't seem to be a very popular unit! Shame, really. It's my favourite XD

    I'm finding past papers relatively easy in comparison to FP2, but on about the same level as M3.

    Good luck for tomorrow everyone!
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    have any of you got the mark scheme for the jan 2013 paper?
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    (Original post by Tedfoo25)
    DE doesn't seem to be a very popular unit! Shame, really. It's my favourite XD

    I'm finding past papers relatively easy in comparison to FP2, but on about the same level as M3.

    Good luck for tomorrow everyone!
    Good to finally see some doing it!

    The past papers do look ok, but I keep making really silly mistakes which cost me a lot of marks. Usually just integrate something wrong or something, it's really annoying! I'm hoping for a lot of 'Show that' questions :P.
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    Hello! I am also taking the DE exam tomorrow!

    After going through the past papers, everything seems okay. You generally get about one 'curve ball' per paper I've found!

    The main thing which can cost me marks are the questions which are very much going through the motions which could cause me to slip with accuracy - this is especially relevant when doing the Simultaneous Differential Equations questions!

    I also think that whilst the 'Mechanics' question that pops up from paper to paper looks horrific most of the time, they're not actually that difficult - has anyone else found the same thing?

    Best of luck!
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    (Original post by Winney5)
    Hello! I am also taking the DE exam tomorrow!

    After going through the past papers, everything seems okay. You generally get about one 'curve ball' per paper I've found!

    The main thing which can cost me marks are the questions which are very much going through the motions which could cause me to slip with accuracy - this is especially relevant when doing the Simultaneous Differential Equations questions!

    I also think that whilst the 'Mechanics' question that pops up from paper to paper looks horrific most of the time, they're not actually that difficult - has anyone else found the same thing?

    Best of luck!
    Yeah haha, or making a really stupid mistake on the integrating factor :/.

    The mechanics questions all seem to be quite similar year on year, some look awful but turn out not to be too bad, you're right.

    Thanks, same to you!
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    Hello again! Just wanted to give some feedback about the exam.

    I ended up doing Question 1 (Second Order stuff), Question 2 (Mechanics question) and Question 3 (First Order with a focus on the Integrating Factor).

    I didn't do the Simultaneous Equations question as there was no real 'checkpoint' for me to check how the question is going!

    All in all, I thought that the exam was pretty straight forward - nothing too off the wall. I think that sound methods were worth the majority of the marks in that paper.

    How did you find it NJam? (and anyone else for that matter?)
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    Don't think it went well, what did you get for your solutions?
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    Pretty average paper overall, I think, aside from the curveball near the end of question 3 (though I got it! ).

    I did 1,3 and 4. I had one sign error at the end of Q4 and I can't have lost more than 7 marks there, probably more like 4, so I'm pretty happy! :cool:

    How did you guys find it? I'd like to know about question 2 (mechanics)!
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    Thought 1 and 4 were standard, still not confident! Any ideas on answers? And 2 and 3 were a bit tricky towards the end, messed up the end of 3, but was relatively simple F=ma up to then
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    Judging by previous grade boundaries and taking into account that this is a higher-scoring June-series paper, we can expect the A to be 63/72 exam + 15/18 coursework. The 90UMS boundary will likely be at 67/72 exam + 16/18 coursework.
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    (Original post by watsam)
    Thought 1 and 4 were standard, still not confident! Any ideas on answers? And 2 and 3 were a bit tricky towards the end, messed up the end of 3, but was relatively simple F=ma up to then
    Don't you mean question 2? That was mechanics and applying N2L.
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    Yes I do mean question 2 sorry
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    (Original post by watsam)
    Yes I do mean question 2 sorry
    How was it overall? What did you have to do?
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    It gave you a driving force, and told you only resistance was a constant resistance force and weight, just have to sub into F=ma, using dv/dt as a to find v in terms of t, then had to convert into x in terms of t, using v=dx/dt. Then changed the resistance force so that it has v^2 in, and had to show that something = v.dv/dx, then find v in terms of t, then draw the graph. I got v^2=1250(10-0.008e^(-k/626)) I think, but the graph looked very wrong.
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    (Original post by watsam)
    It gave you a driving force, and told you only resistance was a constant resistance force and weight, just have to sub into F=ma, using dv/dt as a to find v in terms of t, then had to convert into x in terms of t, using v=dx/dt. Then changed the resistance force so that it has v^2 in, and had to show that something = v.dv/dx, then find v in terms of t, then draw the graph. I got v^2=1250(10-0.008e^(-k/626)) I think, but the graph looked very wrong.
    Did you have a graphical calculator? You can always check it by putting your equation in google graphs.
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    Yeah I did and the y intercept was 111.7 so didn't look right, but we shall see I guess. What were your solutions to 1?
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    I did the exam today and thought it was relatively straight forward but can someone tell me how to prove that x=y had infinitely many solutions in question 4
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    Answers for 1 and 3

    1. i. x = A*e^(-t/2) + B*e^(-t) + 0.3*sin(t) - 0.1*cos(t)

    ii. A = -2/5, B = 1/2
    as t becomes large, x tends to 0.3*sin(t) - 0.1*cos(t) (sketch for large t: http://fooplot.com/#W3sidHlwZSI6MCwi...BlIjoxMDAwfV0-)

    iii. x = -0.1, v = 0.3

    iv. α^2 - 4ω^2 > 0 --> overdamped

    v. x = 0.4*e^(-(x - 10pi)/2) - 0.5*e^(-(x - 10pi))

    3. a. i. y = C*e^(-2x) + 0.25*(sin(2x) - cos(2x))

    ii. C = 9/4 (sketch: http://fooplot.com/#W3sidHlwZSI6MCwi...k5OTk5OTUiXX1d)

    b. i. y = D*e^(-2x) + e^(-x)

    ii. D = 1

    c. at x = 1, y ≈ 0.63860 (=e^(-2)*(2.71862 + 2))

    I can also provide answers to 4 if I can see the question, I can't quite remember all the constants.

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    (Original post by Winney5)
    Hello again! Just wanted to give some feedback about the exam.

    I ended up doing Question 1 (Second Order stuff), Question 2 (Mechanics question) and Question 3 (First Order with a focus on the Integrating Factor).

    I didn't do the Simultaneous Equations question as there was no real 'checkpoint' for me to check how the question is going!

    All in all, I thought that the exam was pretty straight forward - nothing too off the wall. I think that sound methods were worth the majority of the marks in that paper.

    How did you find it NJam? (and anyone else for that matter?)
    I did 1, 3 and 4. I always mess up the mechanics ones. I actually messed up the Sim Equ. one too, but I managed to sort it in the end.

    I agree, nothing too different from the usual. Last part of question 1 is pretty much my only concern at the moment.


    (Original post by SuperCal123)
    I did the exam today and thought it was relatively straight forward but can someone tell me how to prove that x=y had infinitely many solutions in question 4
    Good to hear! I simply rearranged for sint, then stated that sint has infinitely many solutions (since it is periodic) so x=y occurs infinitely many times.

    (Original post by borealis72)
    Answers for 1 and 3

    1. i. x = A*e^(-t/2) + B*e^(-t) + 0.3*sin(t) - 0.1*cos(t)

    ii. A = -2/5, B = 1/2
    as t becomes large, x tends to 0.3*sin(t) - 0.1*cos(t) (sketch for large t: http://fooplot.com/#W3sidHlwZSI6MCwi...BlIjoxMDAwfV0-)

    iii. x = -0.1, v = 0.3

    iv. α^2 - 4ω^2 > 0 --> overdamped

    v. x = 0.4*e^(-x/2) - 0.5*e^(-x)

    3. a. i. y = C*e^(-2x) + 0.25*(sin(2x) - cos(2x))

    ii. C = 9/4 (sketch: http://fooplot.com/#W3sidHlwZSI6MCwi...k5OTk5OTUiXX1d)

    b. i. y = D*e^(-2x) + e^(-x)

    ii. D = 1

    c. at x = 1, y ≈ 0.63860 (=e^(-2)*(2.71862 + 2))

    I can also provide answers to 4 if I can see the question, I can't quite remember all the constants.

    From what I remember, I got the same! Thanks for doing this!

    Quick question, 1v), my friend used t=10pi. It seems like we both used t=0. Who is correct? I would've said t=0 because it stated clearly "for this motion".
 
 
 
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