(Not) Arsey's M3 Edexcel Jan 13 Model Answers (In first post) Watch

Arsey
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Here are some model answers to the M3 thread
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callum Honisett
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So how do people think they did?

Was it a hard paper or did I have a bad day? Had C4 and FP1 first which put me in the wrong mindset I think. Personally thought it was tougher than June '12.
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R4MBO
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(Original post by callum Honisett)
So how do people think they did?

Was it a hard paper or did I have a bad day? Had C4 and FP1 first which put me in the wrong mindset I think. Personally thought it was tougher than June '12.
I also had c4 which I thought was pretty standard, even though I did terribly. As for m3 i actually thought it was fairly simple, no questions really requiring you to use much thought, and a lot where you could be sure of the correct answer as they asked a lot of 'show that' questions. Im predicting similar boundaries for jan 12:

75=100
70=90
65=80.

How did the rest of you find it?
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RichCooper
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(Original post by Arsey)
Here are some model answers to the M3 thread
Thank you!
In question 4b, I'm fairly sure v^2 = 22ag/25 though? Might be a mistake in the cancelling!
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R4MBO
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(Original post by RichCooper)
Thank you!
In question 4b, I'm fairly sure v^2 = 22ag/25 though? Might be a mistake in the cancelling!
I also remember getting the same answer for v^2. How did you find the paper?
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RichCooper
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I thought it was a fairly good paper, looking through it again I think it's gone quite well although I've lost a few marks in places I didn't think to check at the end! Like assuming the SHM question wanted the distance from O and not B, and not taking into account the EPE at M in the very last question


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und
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I thought M was the centre of oscillation in subsequent motion under SHM for the last question. :doh: Other than that it was fine, but that's six marks for one mistake that could have been avoided quite easily had I read the question properly.

Would I be right in assuming this is zero marks due to various incorrect assumptions? I wish I could salvage one or two marks but due to how weird and wrong my working out is I'm just going to assume it's a big fat zero.

\frac{d^{2}x}{dx^2}=\frac{4039}{  45}cos{\omega t}\Rightarrow \frac{dx}{dt}=\frac{4039}{45 \omega}sin{\omega t}

x=-0.07cos{\omega t}\Rightarrow \frac{dx}{dt}=0.07\omega sin{\omega t}

\Rightarrow \frac{4039}{45\omega}=0.07\omega \Rightarrow \omega=35.8081... \Rightarrow v=v_{max}=0.07\omega=2.51 ms^{-1}

I was so proud of that as well. :rolleyes:
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Mastermind2
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This paper was much better than the june 2012 paper, but harder than the jan 2012 paper by some margin. Do people agree?Arsey (or anyone else), I got a different answer to the very last part of the last question, but I'm pretty sure the method was correct(energy considerations). Roughly how many marks will I lose on that? I think I got at least 67/75. Will that be enough for 73/100 UMS, or are we expecting very high boundaries? Thanks
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tornzy
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Are these answers definitely correct? Because if they are........ I flopped reallll bad . And it wasn't even a hard paper :/
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Pitfak
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(Original post by RichCooper)
Thank you!
In question 4b, I'm fairly sure v^2 = 22ag/25 though? Might be a mistake in the cancelling!
looks like it is just a cancelling error; Should be 22ag/25
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IndyJK9
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I made a few mistakes because I had a permanent brain block the whole exam, but considering, it doesn't look to have gone too badly. Maybe lost 5 marks give or take a couple depending on how harsh they punish the errors. All but one were maths or calculator errors. I seemed to have an inability to think straight.
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DJMayes
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Was extremely paranoid about my answers coming out of the exam but they completely (Except getting  v^2 = \frac{22}{25}ag ) match up with yours!
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runningraccoon
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For the last question I misread the question and modelled it as SHM on a vertical string, so 15 marks have gone there
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soempty
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Had a massive timing issue, guess would need to retake this if <75 ums.
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Mastermind2
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What does everyone think the grade boundaries will be? I reckon the following:
A*- 69/75
A- 63/75
B- 56/75
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Varkid
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If for the last part of the ask question, I forgot the strings had e.p.e at M, so said they lost all e.p.e how many marks would I lose?
Also got 22/25 ga for that other question too
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Lili94
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for question 5b was there a similar method involving cos instead of sin? i used cos and although i didn't get the same answer do you think i will get any marks?
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RichCooper
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As long as the forces are resolved correctly, you could've used either angle! I took my angle to be the one next to the particle as well


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DJMayes
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(Original post by RichCooper)
As long as the forces are resolved correctly, you could've used either angle! I took my angle to be the one next to the particle as well


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We're talking about SHM motion, not resolving forces.
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Cellar Door
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This went better than I thought it would

Quite an easy paper I thought, at least compared to the others.

I think I got the first 6 questions mostly right, except for maybe 1 accuracy mistake so maybe dropped 3 marks on that...

Then I think I got all the method marks on the last question, and maybe the right answer to part c), can't remember, so hopefully I dropped another 3 marks or so there...

Hopefully that'll be about 90%?

I did C4 then M3 one after the other and actually found M3 a lot easier oddly :s
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