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Official M5 Edexcel Thread June 2016 watch

1. (Original post by Random1357)
I'm pretty sure there was a square root 2 under sort sign as COM was sqrt(2) from axis
(Original post by 8752)
CoM was root10/2 from axis not root2. CoM was at 1/2,1/2 taking the kink in the wire as the origin.
I had T=pi root(8root10a/3g) or T=2pi root(2root10a/3g)
I did two separate rods with separate COMs and then calculated from that
2. I'm expecting most of these to be wrong; I make a lot of small mistakes, but I feel like I understood every question fairly well, so hopefully I'll get the method marks.

1.) (-6i + 12.5j)
2.) (2sin2t - sint - cos2t)i + (-2sin2t)j
3.) (2i + 3j + 0k), (0i - 2j - 3k)
4.) M[(1/2)r^2 + (1/3)h^2)]
5.) (shown), 2pi*root[(20a)/((3g)(1+root5))]
6.) (shown), V = u*ln5 - 24.5
7.) 3J/(2ma), 3g/(8a) (was negative but needed magnitude), 7mg/8.

For question 5 I had theta as the angle between AB and the vertical, so that's definitely wrong.

For the very last question I did it again in the opposite direction so I have mg/8 and 7mg/8.
3. (Original post by ombtom)
I'm expecting most of these to be wrong; I make a lot of small mistakes, but I feel like I understood every question fairly well, so hopefully I'll get the method marks.

1.) (-6i + 12.5j)
2.) (2sin2t - sint - cos2t)i + (-2sin2t)j
3.) (2i + 3j + 0k), (0i - 2j - 3k)
4.) M[(1/2)r^2 + (1/3)h^2)]
5.) (shown), 2pi*root[(20a)/((3g)(1+root5))]
6.) (shown), V = u*ln5 - 24.5
7.) 3J/(2ma), 3g/(8a) (was negative but needed magnitude), 7mg/8.

For the very last question I did it again in the opposite direction so I have mg/8 and 7mg/8.
Disagree with 2, 5 (maybe a rearrangement), 6 on the second term and 7 final part was mg/8.
4. (Original post by Random1357)
Disagree with 2, 5 (maybe a rearrangement), 6 on the second term and 7 final part was mg/8.
Yeah 2 and 5 I was least confident about.

Relying on this paragraph from the start of every mark scheme for Q7:
"If a candidate makes more than one attempt at any question:
• If all but one attempt is crossed out, mark the attempt which is NOT crossed out.
• If either all attempts are crossed out or none are crossed out, mark all the attempts and score the highest single attempt."

Can anyone remember the questions so I can find my mistakes?
5. (Original post by 8752)
i think 6 marks i'm not quite sure. You couldhave done it using 2 separate centres of mass on each wire but i chose to combine the com to make it easier.Attachment 554191
that's what i did!!!
6. (Original post by borgunblue)
What are the odds that the board will accept both cases for cylindrical shell? The answer I got for closed ends is
(M(3r^3+6hr^2+6rh^2+4h^3))/(12(r+h))
(Original post by Euclidean)
I don't think they made it very clear. I actually did the same as you and crossed it out after.

I think they should give credit for a method with closed ends but they probably won't award 10/10.
The formula for the moment of inertia of a cylindrical shell is in the formula book, linked to the M of I of a hoop, so that is the clue that this cylindrical shell shouldn't be closed at the ends.
7. (Original post by ombtom)
I'm expecting most of these to be wrong; I make a lot of small mistakes, but I feel like I understood every question fairly well, so hopefully I'll get the method marks.

1.) (-6i + 12.5j)
2.) (2sin2t - sint - cos2t)i + (-2sin2t)j
3.) (2i + 3j + 0k), (0i - 2j - 3k)
4.) M[(1/2)r^2 + (1/3)h^2)]
5.) (shown), 2pi*root[(20a)/((3g)(1+root5))]
6.) (shown), V = u*ln5 - 24.5
7.) 3J/(2ma), 3g/(8a) (was negative but needed magnitude), 7mg/8.

For the very last question I did it again in the opposite direction so I have mg/8 and 7mg/8.
Dammit

Well done btw

Q4 didn't go my way and now I think my Q6 is messed up too
8. (Original post by Euclidean)
Dammit

Well done btw
Well done? I got a few answers wrong... It was still a fun exam though

Is M5 necessary for your uni offer? (Sorry if you've already told me.)
9. Here is my solution to question 5 about the period of oscillation. My previous upload I forgot to flip the g and a in the last step so here is the updated correct version.

10. (Original post by ombtom)
Well done? I got a few answers wrong... It was still a fun exam though

Is M5 necessary for your uni offer? (Sorry if you've already told me.)
I think my Q2(b) is wrong, but I couldn't figure out how. Q4 was bad I did a flippin rod instead of a cylindrical shell and Q6 might be fine for a few M marks hopefully.

I might have around 60/75 which is probably not gonna make M5 a strong module at all

I don't think so, I should already have enough modules to make up 540 for A*A* (Further Maths and Add Further Maths) but I really wanted M5 to be one of my stronger modules, now I gotta put a lot of work into S4 on friday
11. (Original post by 8752)
Here is my solution to question 5 about the period of oscillation. My previous upload I forgot to flip the g and a in the last step so here is the updated correct version.

I didn't calculate the COM of the body and instead did two separate COM's with moments about the axis. Problem is, my answer is different to yours ...
12. (Original post by Euclidean)
I think my Q2(b) is wrong, but I couldn't figure out how. Q4 was bad I did a flippin rod instead of a cylindrical shell and Q6 might be fine for a few M marks hopefully.

I might have around 60/75 which is probably not gonna make M5 a strong module at all

I don't think so, I should already have enough modules to make up 540 for A*A* (Further Maths and Add Further Maths) but I really wanted M5 to be one of my stronger modules, now I gotta put a lot of work into S4 on friday
The boundaries for M5 are strange; last year was 68 for an A but the average is 57. Hopefully it'll return to the low 60s but I have no idea.

"Damn, S4? S1 is hard enough." A*A* is amazing though, well done.
13. (Original post by ombtom)
The boundaries for M5 are strange; last year was 68 for an A but the average is 57. Hopefully it'll return to the low 60s but I have no idea.

"Damn, S4? S1 is hard enough." A*A* is amazing though, well done.
I'm hoping Q4 stumped quite a few of the candidates making the boundaries a little nicer. I was worried about rotation but rotation is what I seemed to get right in the end From what people are saying here too, the L shape wasn't very easy either...

1) < -6 , 12.5 >

2) < sin t , cos 2t >

3)
a) < 2 , 3 , 0 >
b) < 0 , -2 , -3 >

4) M/6 ( 3r^2 + 2h^2 )

5) Same as Random1357

6) u ln(5) - 19.6

7) don't remember the J thing, but got mg/8 in the lastest part.
15. (Original post by Euclidean)
I didn't calculate the COM of the body and instead did two separate COM's with moments about the axis. Problem is, my answer is different to yours ...
In that case you needed to take moments about A and this is what I would have done:

16. (Original post by gagafacea1)

1) < 6 , 12.5 >

2) < sin t , cos 2t >

3)
a) < 2 , 3 , 0 >
b) < 0 , -2 , -3 >

4) M/6 ( 3r^2 + 2h^2 )

5) Same as Random1357

6) u ln(5) - 19.6

7) don't remember the J thing, but got mg/8 in the lastest part.
You've found r for Q2) and they asked for v

I agree with Q1),Q7),Q6),Q3) though!
17. (Original post by 8752)
In that case you needed to take moments about A and this is what I would have done:

Ah okay! I'm glad that this is an actual method though. I got scared that I'd done something that doesn't actually work! Worst case I'll get M marks

Thanks!
18. (Original post by Euclidean)
You've found r for Q2) and they asked for v

I agree with Q1),Q7),Q6),Q3) though!
SHOOT!!!
19. (Original post by Euclidean)
You've found r for Q2) and they asked for v

I agree with Q1),Q7),Q6),Q3) though!
Okay but like seriously?? why did they do that??? I am 100% sure the person who wrote this question knew people would forget to differentiate and lose marks there.
20. (Original post by gagafacea1)
Okay but like seriously?? why did they do that??? I am 100% sure the person who wrote this question knew people would forget to differentiate and lose marks there.
A levels are very petty sometimes

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