Edexcel M4 Exam Discussion Thread [June 5th] Watch

s.c.a1
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#41
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For anyone who has done M1 i have a question: I am getting very confused betweeen when the acceleration due to gravity should be negative and when it should be positive? if i make my positive direction upwards, will a/g always be negative because gravity acts downwards or does it depend on the question??
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Vesniep
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(Original post by s.c.a1)
For anyone who has done M1 i have a question: I am getting very confused betweeen when the acceleration due to gravity should be negative and when it should be positive? if i make my positive direction upwards, will a/g always be negative because gravity acts downwards or does it depend on the question??
If your positive direction is upwards you take the acceleration due to gravity negative. If your positive direction is downwards ......positive.I think it doesn't depend on the question. It only depends on where your positive direction is.
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s.c.a1
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(Original post by Vesniep)
If your positive direction is upwards you take the acceleration due to gravity negative. If your positive direction is downwards ......positive.I think it doesn't depend on the question. It only depends on where your positive direction is.
thankyou!!
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Vesniep
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It would be interesting to think the resisted motion of a particle in circular motion(connection of m3 and m4). We can not just ignore air resistance when we want to find the minimum velocity for which the particle will perform complete circle.I think a case like this can be solved with a differential equation(we can also see the motion of the particle with respect to time).What do you suggest to do?
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physicsmaths
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(Original post by Vesniep)
It would be interesting to think the resisted motion of a particle in circular motion(connection of m3 and m4). We can not just ignore air resistance when we want to find the minimum velocity for which the particle will perform complete circle.I think a case like this can be solved with a differential equation(we can also see the motion of the particle with respect to time).What do you suggest to do?
If the resistance to motion is prorotional to speed velocity then yes it would probably be a differential equation solved via an integrating factor.


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physicsmaths
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I could be wrong though.


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simonli2575
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#47
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(Original post by Vesniep)
It would be interesting to think the resisted motion of a particle in circular motion(connection of m3 and m4). We can not just ignore air resistance when we want to find the minimum velocity for which the particle will perform complete circle.I think a case like this can be solved with a differential equation(we can also see the motion of the particle with respect to time).What do you suggest to do?
(Original post by physicsmaths)
If the resistance to motion is prorotional to speed velocity then yes it would probably be a differential equation solved via an integrating factor.


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I think it would be impossible though, because it's kind of like trying to solve the equation for a pendulum with large angle of oscillations
\frac{d^2\theta}{dt^2} = -\frac{g}{l}sin(\theta)
But then you make it harder by adding resistance to it.
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Vesniep
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(Original post by physicsmaths)
If the resistance to motion is prorotional to speed velocity then yes it would probably be a differential equation solved via an integrating factor.
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Do you know to solve differential equations different from 1st and 2nd order? Because the equation of motion is m*dv/dt=-mkv-mgsinθ =>
d^2θ/dt^2=-kdθ/dt-(gsinθ)/r, where θ is the angle with the verticle and we want to find θ(t) .....and I can't solve it.I can't even solve when κ=0 (all these are unknown differential equations)and it is the motion we all do in m3 exercises but we only use energies ....we don't know how the particle moves with respect to time.
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simonli2575
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(Original post by Vesniep)
Do you know to solve differential equations different from 1st and 2nd order? Because the equation of motion is m*dv/dt=-mkv-mgsinθ =>
d^2θ/dt^2=-kdθ/dt-(gsinθ)/r, where θ is the angle with the verticle and we want to find θ(t) .....and I can't solve it.I can't even solve when κ=0 (all these are unknown differential equations)and it is the motion we all do in m3 exercises but we only use energies ....we don't know how the particle moves with respect to time.
I don't think we can solve it, though you can if the angle is small... in M5.
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Vesniep
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(Original post by simonli2575)
I don't think we can solve it, though you can if the angle is small... in M5.
Maybe we can't . But there is probably some kind of solution to this.If you find θ(t)(you have to use initial velocity and θ(0)=0 to find arbitrary constants) then you can find the velocity(v=r*dθ/dt) of the object for θ=π,3π,5π,... for some θ=(2n+1)pi v<0 so you will take the velocity of the previous θ=(2n-1)pi and see if T>0 for this velocity. If yes ,the particle has made n-1 circles ,if not you take the previous θ........ and you do this (or the program,which can also solve the dif. equation maybe)until T>0. So in this way you can find how many circles it did.Please correct me if I am wrong.
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Melanie Leconte
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(Original post by Vesniep)
exams i give: c1-c4, fp1-fp3,m1-m4,s1
When I sent them an email asking for specific information they just gave me a link which had information about the mathematics course and said to me that 5 over 75 of the applicants of my country enter the university(nice to be informed this...)... in other way ''we don't really want greeks'' or ''greeks are pretty much stupid(which unfortunately it is actually true) '' . Sometimes I just don't like their snobbish attitude .

Don't read to much into it Vesniep, MIT gave me a similar answer...they only take 3% of the internationals. It is meant to warn you that the competition is fierce.
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Vesniep
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(Original post by Melanie Leconte)
Don't read to much into it Vesniep, MIT gave me a similar answer...they only take 3% of the internationals. It is meant to warn you that the competition is fierce.
I misunderstood the meaning, I know.I also know that the competion is fierce as you said, but that doesn't mean that international students should have less chance than English students. I changed my mind about this issue though.
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Melanie Leconte
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(Original post by Vesniep)
I misunderstood the meaning, I know.I also know that the competion is fierce as you said, but that doesn't mean that international students should have less chance than English students. I changed my mind about this issue though.

I am glad you have changed your mind.
Good luck
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Vesniep
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Is there any UMS converter for M4 Jun 2009(Edexcel).The converter I have ,only has years after Jan 2010.Thank you.
Also, why is this thread so dead? I think that I am talking to myself right now and noone is going to answer ,never.
We are having M4 in a month,does anybody care or am I the only one sitting this module?
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ThatPerson
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(Original post by Vesniep)
Is there any UMS converter for M4 Jun 2009(Edexcel).The converter I have ,only has years after Jan 2010.Thank you.
Also, why is this thread so dead? I think that I am talking to myself right now and noone is going to answer ,never.
We are having M4 in a month,does anybody care or am I the only one sitting this module?
I'm also sitting M4, but I haven't got round to doing past papers yet. Too busy doing other things.
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Vesniep
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(Original post by ThatPerson)
I'm also sitting M4, but I haven't got round to doing past papers yet. Too busy doing other things.
So when are you going to start?
Bad news are : Past papers are so few and they are not that easy (I can say that this is the most difficult module at least for me). The most difficult chapters are Relative Motion and Collisions in 2 dimensions(when you have to do scalar products and stuff like this, they can easily get difficult).However, all the other chapters are ridiculously easy (Chapters 3 to 5). Does anybody now any other recources for this module?
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ThatPerson
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(Original post by Vesniep)
So when are you going to start?
Bad news are : Past papers are so few and they are not that easy (I can say that this is the most difficult module at least for me). The most difficult chapters are Relative Motion and Collisions in 2 dimensions(when you have to do scalar products and stuff like this, they can easily get difficult).However, all the other chapters are ridiculously easy (Chapters 3 to 5). Does anybody now any other recources for this module?
Probably right after M3. Personally I find Stability the hardest topic - not conceptually, but I dislike the geometry, especially in the more complicated questions.
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physicsmaths
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(Original post by ThatPerson)
Probably right after M3. Personally I find Stability the hardest topic - not conceptually, but I dislike the geometry, especially in the more complicated questions.
Yh Im gona revise for it at the end of the month. Aint done any practice for it yet as I am not really bothered about the module itself as it doesnt matter haha.


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Vesniep
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(Original post by physicsmaths)
Yh Im gona revise for it at the end of the month. Aint done any practice for it yet as I am not really bothered about the module itself as it doesnt matter haha.
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What do you mean? Don't you have an offer from Cambridge and doesn't this offer demands A* in Further Maths?Or you just take this unit as Further maths additional that are not required for your offer?
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physicsmaths
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(Original post by Vesniep)
What do you mean? Don't you have an offer from Cambridge and doesn't this offer demands A* in Further Maths?Or you just take this unit as Further maths additional that are not required for your offer?
I am just taking an extra unit. Ive learnt parts of M4 and M5. My Maths and FM alevel is made up of these modules
C1 C2 C3 C4 S1 S1 FP1 FP2 FP3 M1-3
I already have 100 in M2 so I only need 85 in two more A2 modules which I should get easily in FP2 and FP3 M3.


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