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# Edexcel - M3 - 18th May 2016 watch

1. (Original post by Ayman!)
SHM ones and elastic string ones are different for me. Everything else seems to be okay.
what did you get for the SHM ones?
2. (Original post by Krollo)
I think it was mainly so we got omega to set us up for the last bit

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Yeah probably

(Original post by Student403)
Fair point. Seems free marks in retrospect
Exactly why I was doubting myself! Honestly this is why i have a love-hate relationship with Show-that questions, on one hand I love knowing what my answer should be, but on the other, no matter how much I put in, I still think it's not enough.
3. (Original post by Velywen)
To prove the SHM, it's the same thing as in the beginning, except the mass of the particle is 0.8 kg instead of 0.3 kg (if that was right) and also it starts from origin (so it's a sin function).

For amplitude, calculate the velocity at the centre of oscillation using conservation of momentum.

0.3*(Vmax of the initial oscillation) = 0.8(Vmax of new oscillation)

Vmax of new oscillation = Amplitude*angular speed.

Angular speed comes from the SHM equation, thus allowing you to calculate the amplitude.
0.5*
4. (Original post by gagafacea1)
Yeah probably

Exactly why I was doubting myself! Honestly this is why i have a love-hate relationship with Show-that questions, on one hand I love knowing what my answer should be, but on the other, no matter how much I put in, I still think it's not enough.
Yeah exactly xD
5. (Original post by nthyy)
what did you get for the SHM ones?
24/49 = 0.490 and 8 hours 19 mins. How did you do the elastic string one? It was so easy yet I might have messed it up - got 11/16. These are the only two that could pretty much make or break my paper
6. (Original post by Student403)
0.5*
Yeah that, im terrible at remembering numbers.
7. (Original post by dsefton)
How many marks am I likely to lose for saying T>0 rather than T>=0 for question 6b (show that AB>=l/2) given that all my other working was correct? Also am I likely to lose a mark as I put -1/3N for the 1st question and it apparently asked for the magnitude?
I did the same for the first question... Hoping I won't lose any marks but they can't penalise anymore than 1 or 2 if we do... the method to get there was right at most we probably lose an Accuracy mark? Hopefully.

With regards to the T>=0 I have no idea, logically again it might be one or 2 but shouldn't be too many, not enough to affect a grade overall unless you are borderline... hopefully someone agrees with me on this though...
8. (Original post by Ayman!)
24/49 = 0.490 and 8 hours 19 mins. How did you do the elastic string one? It was so easy yet I might have messed it up - got 11/16. These are the only two that could pretty much make or break my paper
Did get 0.490 meters per hour?
wht was the time period you used
9. So.... Is anyone going to make a hitler video?
10. This is how inconsistant edexcel is. In the UK paper in one question they used T>=0 and the other question the use T>0, they really need to sort it out!

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11. (Original post by physicsmaths)
This is how inconsistant edexcel is. In the UK paper in one question they used T>=0 and the other question the use T>0, they really need to sort it out!

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Exactly. Although my personal vendetta is one year it will be >= and the next year > . We need consistency!!!
12. (Original post by Velywen)
So.... Is anyone going to make a hitler video?
Do you think it's worthy of a Hitler video?
13. (Original post by physicsmaths)
This is how inconsistant edexcel is. In the UK paper in one question they used T>=0 and the other question the use T>0, they really need to sort it out!

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Lmao I noticed that. Very slack of them.

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14. (Original post by nthyy)
yes and i spent most of the time understanding the question (sigh but i got it wrong)
i remember some of the answers but most of them are probably wrong, idk i think i really screwed up my paper

horizontal circular motion - prove
SHM - a) prove + b) period (is it 2pi√a/g?)
SHM (ladder) - a) speed(1.54mh-1?) + b) length of time (sigh idk)
vertical circular motion - a) prove + b) distance AC? (i think i got 0.6m)
gravitation - a) prove + b) U=√(2/21)gR
elastic string - a) prove OB<l, b) distance OB (15l/16)
centre of mass - a) prove CoM of cone + b) angle between OA and c) vertical (38.2°) + d) value of k (11/4?)

now that i think about it, the paper was pretty straightforward except for the SHM part b one!!!
my answers are same as yours !! you will be fine
except the part b ladder got us confused
15. (Original post by Ayman!)
24/49 = 0.490 and 8 hours 19 mins. How did you do the elastic string one? It was so easy yet I might have messed it up - got 11/16. These are the only two that could pretty much make or break my paper
i found distance AB by conservation of energy, where loss in EPE = work done against friction (AB= 5l/16)
then i subtract distance AB from distance OA (which is 5l/4) to find distance OB
(5l/4 - 5l/16 = 15l/16)
16. (Original post by Ayman!)
24/49 = 0.490 and 8 hours 19 mins. How did you do the elastic string one? It was so easy yet I might have messed it up - got 11/16. These are the only two that could pretty much make or break my paper
I think you should have forgotten the pie
v= 24pie/49 = 1.54... mhr^-1

When you change Period into angular velocity there is a pie involved

If you hv forgot the pie for angular velocity, your answer for part B is most likely wrong. Your method is exactly same as mine i have checked, apart from the pie you missed.
17. (Original post by physicsmaths)
This is how inconsistant edexcel is. In the UK paper in one question they used T>=0 and the other question the use T>0, they really need to sort it out!

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I was confused because from past papers I'd assumed they were always non-strict

In terms of theory, surely they are non-strict?
18. (Original post by ombtom)
Do you think it's worthy of a Hitler video?
I'm pretty sure difficulty is no longer a pre-requisite for a Hitler video

19. (Original post by Euclidean)
I'm pretty sure difficulty is no longer a pre-requisite for a Hitler video

I was going to say that but couldn't word it so eloquently.
20. (Original post by Euclidean)
I'm pretty sure difficulty is no longer a pre-requisite for a Hitler video

I believe they made MORE than 1 for C1... I have seen at least 3...

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