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# Edexcel Mathematics: Mechanics M3 6679 01 - 17 May 2017 [Exam Discussion] watch

• View Poll Results: How did you find this exam?
Amazing!
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Good
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OKAY.
44
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HORRIBLE PAPER!!
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1. (Original post by dididid)
Attachment 647496why is d=r on this? Q3b jan 03
if you draw it, you should be able to see it.
2. (Original post by dididid)
could you please explain it to me? i don't know how d=r as i know the c of mass has to lie within the hemisphere but why on the plane face?
Let's say the solid lies with the cylinder horizontal. The object is in equilibrium as the end of the surface of the hemisphere touches the ground. The centre of mass must lie along the vertical from the reaction point e.g. the plane face. As a result d ends up being the same as the radius since the COM is at the plane face.
3. Could someone help me on the centre of mass of a uniform llamina in the form of a sector of a circle, radius r and centre , which subtends an angle 2alpha.
4. (Original post by TrueDAN)
I found them to be about the same as papers - guess it is different for everyone. I enjoyed paper D because it had a really nice gravitational problem on the moon and a good COM question that has came up before.
cheers
5. When a particle is attached to the string rather than threaded the tension are different in each part of the string, right?

TrueDAN solC Major-fury
6. (Original post by TSRUser12345)
When a particle is attached to the string rather than threaded the tension are different in each part of the string, right?

TrueDAN solC Major-fury
7. (Original post by TSRUser12345)
When a particle is attached to the string rather than threaded the tension are different in each part of the string, right?

TrueDAN solC Major-fury
Yup I think thats right - i can remember I got caught out by this once and so have applied that rule onwards and seems to have held true
8. Think Im going to be signing off now - gonna just relax and then hopefully be able to get some sleep - all the best for tomorrow guys, lets go and smash it!!
9. (Original post by TrueDAN)
Think Im going to be signing off now - gonna just relax and then hopefully be able to get some sleep - all the best for tomorrow guys, lets go and smash it!!
Thanks and good luck!
10. For Jan 10 question 5, why is the least tension in the string at v=0 ?
11. (Original post by Major-fury)
Could someone help me on the centre of mass of a uniform llamina in the form of a sector of a circle, radius r and centre , which subtends an angle 2alpha.
There's an example on it in the book
12. (Original post by AAls)
For Jan 10 question 5, why is the least tension in the string at v=0 ?
The tension is least at the highest point reached by the particle and greatest at the lowest point. In this motion the string is taut throughout so the highest point would be when the speed of the particle v=0.
13. When asked to prove centre of mass of a solid using integration, can I form an equation then use c4 methods or do I have to use the strips?
14. Unofficial mark scheme for today's paper?
(Original post by solC)

Edexcel past papers
http://www.physicsandmathstutor.com/...rs/m3-edexcel/

Solomon papers
http://www.physicsandmathstutor.com/...rs/m3-solomon/

Practice papers from crashMATHS
http://crashmaths.com/a-level-practice-papers/
Feel free to share any tips or ask questions
15. I thought the exam was harder than some recent papers for sure. Not outrageous but certainly a few non-standard aspects.
16. Pretty standard! Think grade boundaries will reflect this though. Managed to mess up the first question (did volume of revolution) and the COM question (forgot about Base of cylinder looool) but had enough time to sort these out. Hope it went okay for you all!
17. What did you get for the time in the last question?
18. Thought it was pretty standard with some abstract questions - incline plane calculus was unusual and so was c.o.m. LAst part of SHM required some thought too.
19. (Original post by .floyd.)
What did you get for the time in the last question?
1.02s
SHM from 0.5m to -0.4m then +0.72s
20. If anyone here did the IAL paper I would be happy to discuss. Also our exam had a 9 mark question from M2 (I don't think I can go into specifics rn) but can they do that? (It wasn't a general idea being used but a straight up question that you would expect in an M2 exam)

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