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The official M3 discussion thread - 7th June 2005

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Reply 20

lilbug

hmm ok i get it.
thanks for the notes too, widowmaker. i'd rep you if i could.

Reply 21

mysterious_grl

hi..can anyone plz do mock paper qs 7 except for a...thnx

Reply 22

green_eyes

i keep thinking i understand everything but the more i do the more i go wrong! i got 100% on a paper yesterday and 53% on a paper today! i keep making stupid errors. circular motion is my hardest topic, and i really really hope there isn't any difficult integration or differentiation in there i haven't looked at it since p3 though i really should before p4....
omg. im going to go and panic quietly now...

Reply 23

LoNdOnDeViL

Im taking the exam tomorrow and so far it looks to be very hard :/ i didnt remember it being is hard :frown:

Looks like ill be doing an all nighter trying to get a pass on this one :frown:

GL ALL OF YOU!!!

Reply 24

Christophicus

LoNdOnDeViL

Im taking the exam tomorrow and so far it looks to be very hard :/ i didnt remember it being is hard :frown:

Looks like ill be doing an all nighter trying to get a pass on this one :frown:

GL ALL OF YOU!!!

I strongly advise against it.

Reply 25

LoNdOnDeViL

I know thats what everybody says, but i just cant seem to get to grips with most of the concepts. Im going through your notes now =) There nice thanx

Reply 26

Christophicus

Guys if you don't understand anything i'm here to help.

Here are some extra notes.

Particle on a banked plane travelling in a horizontal circle.
- acceleration acts inwards towards the centre.
- friction acts up the plane if the particle is about to slip.
- friction acts down the plane if the particle doesn't slip.

Conical pendulum
- occurs when a particle moves in a horizontal circle attached to a string whose other end is fixed at a point A vertically above the centre of the horizontal circle O.
- vertically: Tcosθ = mg
- horizontally: Tsinθ = ma

Reply 27

Lucky Penny

ah mock paper question 5b!!! has anyone done it?

Reply 28

Christophicus

Lucky Penny

ah mock paper question 5b!!! has anyone done it?

yes. I have. See first post in this thread for a link to the answers.

Reply 29

Lucky Penny

yeah i've got the answers but i have no idea to work out the extension of the string to calculate the E.P.E of the final position..?!

Reply 30

Christophicus

Lucky Penny

yeah i've got the answers but i have no idea to work out the extension of the string to calculate the E.P.E of the final position..?!

use answer calculated in part a.
This is equal to 1.7991m ≈ 1.80m

EPE at final position
= λx²/2L
= 120(1.7991+0.5)²/6
(since the spring is compressed by 0.5m already and has to rise 1.80m as well.)

Reply 31

Lucky Penny

hmmm ok not sure I'd see that in an exam.. and is there an extension in the initial posiiton?

Reply 32

Lucky Penny

Yes i'v got it finally! Just took somethinking about (and a neat diagram). Cheers for your help widowmaker!

Reply 33

Sparkling_Jules

Just wondering if anyone has ever seen an exam question about the COM of mass of a lamina in an M3 exam. You know the sort described as an area under a graph.

Reply 34

Christophicus

Sparkling_Jules

Just wondering if anyone has ever seen an exam question about the COM of mass of a lamina in an M3 exam. You know the sort described as an area under a graph.

yep. Came up in jan 05.
I'm really annoyed with edexcel cos the spec says for m3 you only need to know differentiation/integration for c1-c3 but integration of trigonometric functions is c4????

Reply 35

ziya_the_king

can please some1 show me how the hell can you do this?

m3 may 03.JPG55.8KB

Reply 36

Lucky Penny

You got anywhere with it or you stuck on all of it?

Reply 37

ruzaika

HIII does anyone have the m3 detailed mock answers. especially for question 4(A) where they ask us to prove that it is SHM....in dire need of it :frown:

. what is theory for questions like these. i mean i can do the horizontal and vertical ones but these>> pls. just what i need on the eve of the exam :mad:

thanks

Reply 38

Lucky Penny

Let the tension is AP = T and the tension in PB = S

Resolving vertically:
Tcosσ = mg + Scosσ

Horizontally:
Tsinσ + Ssinσ = mrω²

From triangle AOP, cos σ = 3/4, sin σ = √7/4

So vertically: T = 4(mg +3S/4)/3
= 4mg/3 + S

horizontally: T = 4(√7mlω² /4 - S√7/4) / √7
= √7mlω² - S√7
= mlω² - S

Equating:

T - 4mg/3 = mlω² - T
2T = mlω² + 4mg/3
6T = 3mlω² + 4mg
= m(3lω² + 4g)
T = 1/6 m (3lω² + 4g)

Hope that helps, i know it's really longwinded

Reply 39

Sparkling_Jules

For question 6 Jan 02, how do you prove it is SHM? I've got the amplitude, I've got a constant w at A and B using v^2 = w^2(a^2 + x^2). But usually they want a=w^2x.