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# Edexcel M2/M3 June 6th/10th 2013 watch

1. Can we use column vectors for centre of gravity questions and all?
2. (Original post by Riley F.)
My method is slightly different to the mark scheme's, so i'm not quite sure what they've done with the cos(a).

You found the COM for part a). Now another mass has been added to the system. That means the COM has moved, so you need to find the new COM in order to work backwards and find the mass of the particle. The question said that the lamina is suspended from S. Therefore, it will rotate/swing until the new COM lies directly below S - that is the same as drawing a straight line from S to the new COM. Once you know how far away the COM is from the centre of the circle (which you can because you know that tan(a) = 5/6), you can work out how far away it is from P. Once you know that distance, you can take moments (about P) to find k.
I thought the line would be a bit slanted and when I looked at the MS I couldnt work out how they got cosa. If it lies horizontal then that makes it a bit simple than what I was try to do since an hour lol
thanks again!
3. Can anyone help me with june 2012 M2 paper question number 3b? I dont understand why they use Fcos75
Thanks
4. Does anybody have a link for M2 jan 13? I looked through thread but didn't find it, sorry if I missed a link D:
5. June 2011 question 5b - why do they not take into account GPE? They only take into account change in KE but I thought you had to do the total energy change...
6. (Original post by alwayslast)
Does anybody have a link for M2 jan 13? I looked through thread but didn't find it, sorry if I missed a link D:
http://www.scribd.com/doc/126760650/...ary-2013-M2-QP
7. Thanks
8. (Original post by AS01)
Can anyone help me with june 2012 M2 paper question number 3b? I dont understand why they use Fcos75
Thanks
Well they have asked to find the vertical component of the force acting on the rod at A.
Now the rod is in equilibrium so upward forces=downward forces.

One upward force is the component of F upwards. Now if we draw a horizontal at B (where F acts) you will get an angle F makes with the horizontal. Then draw the vertical and it will strike you why they use Fcos75 (or Fsin15)

Hope you get it.
9. (Original post by StUdEnTIGCSE)
Can we use column vectors for centre of gravity questions and all?
that's what I do
10. Does it matter which way we assume the particles travel in the collision questions!
11. (Original post by Anonymous1717)
June 2011 question 5b - why do they not take into account GPE? They only take into account change in KE but I thought you had to do the total energy change...
Well if you consider the component of weight down the slope in addition to friction as forces doing work then you do not need to consider GPE.

Loss of KE= Gain in GPE + work done by friction

is the same as

Loss of KE = (forces acting down the plane) * distance
12. (Original post by Boy_wonder_95)
that's what I do
But my teacher never mentioned it!

Good now, it makes it more neater and faster.
13. (Original post by FLLF)
Does it matter which way we assume the particles travel in the collision questions!
I reckon it does matter!

If they ask to find speed then you must take care of the direction as speed is always greater than zero. So speed is not equal to negative velocity or like -3(u+e).
14. (Original post by StUdEnTIGCSE)
But my teacher never mentioned it!

Good now, it makes it more neater and faster.
It does it in the book doesn't it?
15. (Original post by FLLF)
Does it matter which way we assume the particles travel in the collision questions!
It doesn't matter. If your speed turns out to be negative all it means is that it is travelling the other way round.
16. (Original post by Boy_wonder_95)
It does it in the book doesn't it?
Ah yes I remember...I don't use the textbook much...
So you can even use the column vectors instead of i and j notations nah?
17. (Original post by StUdEnTIGCSE)
Ah yes I remember...I don't use the textbook much...
So you can even use the column vectors instead of i and j notations nah?
Yes, sitting M2 in yr 12?
18. (Original post by Boy_wonder_95)
Yes, sitting M2 in yr 12?
Life will be much easier now. i and j notations RIP!

I'm in yr 11, not 12.
19. (Original post by StUdEnTIGCSE)
Life will be much easier now. i and j notations RIP!

I'm in yr 11, not 12.
still 17
20. (Original post by Boy_wonder_95)
still 17
Well is that a good thing?
You have students like L'Evil Fish sitting C4 at 16.

But I'm doing Further also and with no Jan exams M2 is inevitable this year, but its kinda easy.

Are you doing Further Maths?

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