* Applied Maths * predictions / discussion / aftermath (1 thread only please)

magicianz

Quick question for anyone doing Q8, in the 2007 question the very last part of the answer is v=4w, v = 5.87 m/s, where did they got the 4??

Is it because the diameter of the circular movement of the corner 'C' is 4? Just thought of that while posting >.>

link to marking scheme/paper http://www.examinations.ie/archive/markingschemes/2007/LC020ALPO00EV.pdf

KoolAidRelic

LilMissCiara wrote: »

but the marking scheme doesn't have my method (I checked the alternative solutions as well)...

My teacher is one of the (few!) correctors for the paper and told us that the "alternative" solutions given in the marking scheme aren't all the alternative ones. At the marking conference yoke they might have came across a huge amount of other ways to solve them, but they don't all make it into the published marking scheme.

Any valid method will get the all the marks.

ride-the-spiral

It is indeed because the radius of the circle on which c rotates is 4, as v=radius x w

HOPEd

I really want to get an A1 cause I dont think I got enough points:( (never thought Id be relying on Applied maths:rolleyes:)
Im plannin on doin q 1,2,3,4,5 and 10 (cause those are the only ones our teacher did with us) Has anyone got any tips on how I could study??? I need a really good study plan ...PLESE help

aranciata

I'm doing 2004 Q2a at the moment... can anyone tell me why is the 22sinA=18sin45? Shouldn't the i values be equal, seeing as the bird has to counteract the push east it's getting from the wind? Doesn't the j value of the wind not help the bird?

KoolAidRelic

aranciata wrote: »

I'm doing 2004 Q2a at the moment... can anyone tell me why is the 22sinA=18sin45? Shouldn't the i values be equal, seeing as the bird has to counteract the push east it's getting from the wind? Doesn't the j value of the wind not help the bird?

That's the sine rule, not equating j's.

I did that question yesterday and said that the i's should be equal and opposite, which would be: 22cosA = 18cos45 (your way).
That'll give A as 55 degrees (North of East), whereas the marking scheme has 35 degrees (East of North). Either way works fine.

aranciata

KoolAidRelic wrote: »

That's the sine rule, not equating j's.

I did that question yesterday and said that the i's should be equal and opposite, which would be: 22cosA = 18cos45 (your way).
That'll give A as 55 degrees (North of East), whereas the marking scheme has 35 degrees (East of North). Either way works fine.

Ah I get it now. I got 55 degrees too, the marking scheme made it look like I was doing it wrong - we've never used sin rules! Thanks!

aranciata

I know i'm asking a lot of questions but this will be the last time I EVER will! Looking at the 2002 paper, there's a simple harmonic motion question in the middle of Q4... my class has never covered that, and we've only covered 6 questions so there's not gonna be any choice tomorrow... could they do that again?

epicwinning

aranciata wrote: »

I know i'm asking a lot of questions but this will be the last time I EVER will! Looking at the 2002 paper, there's a simple harmonic motion question in the middle of Q4... my class has never covered that, and we've only covered 6 questions so there's not gonna be any choice tomorrow... could they do that again?

They could. Even if you didn't cover it, all the formulae for simple harmonic motion are in the log tables anyway...

ride-the-spiral

I wouldn't worry about it. Apparently at the teacher's conference there was much anger towards the choice so I doubt they'd do something like that again.

LilMissCiara

Anyone in the same boat?

I do a question (say Q1), correct it and do well (well for me is 35m+). I move to the next year and get about 15m (in Q1)...

Tomorrow's paper better be fúcking good (and by good I mean have the questions I can do good in!)

aranciata

LilMissCiara wrote: »

Anyone in the same boat?

I do a question (say Q1), correct it and do well (well for me is 35m+). I move to the next year and get about 15m (in Q1)...

Tomorrow's paper better be fúcking good (and by good I mean have the questions I can do good in!)

That's definitely happening to me. I'm planning on leaving Q1 until the end cause it can be the most frustrating..

I'm focusing on Q2, Q3 (especially the inclined plane questions - my favourite) and Q10 cause they're quite formulaic and the methods can be pretty much learned off... hope I scrape a B2!

ride-the-spiral

Well you're recommended to never start with question 1 as it can be the most deceptive. And in terms of your timing problem, limit every question to 25 minutes, and if you finish a question in less time you can go back and finish any one that is incomplete. I know in an exam it seems so counterintuitive to just leave the question after 25 minutes, especially if you feel like you've almost got the answer, but just do it. In the end, you'll get more marks for drawing the diagrams and starting the equations of the next question than for the amount of time you might spend finishing off the algebraic part of your current question.

EDIT: I just realised that was not what you were asking at all... :P

deiseguuy93

this is it guys! tomorrow is D-day and i would like to say good luck to all of ye! And have a great sessions afterwards!

LilMissCiara

I was using 1 as an example... It happens on all of them!

HOPEd

Pulleys and Wedges

Can anyone explain the concept of relative acceleration to me please? ... I dont get it...:eek:

Geog ariphic

2009: q10b (ii)

The marking scheme uses a tan formula in integrating, but i cannot follow it at all, and i ahve tried.
Can anyone shed light on what is going on in this one please?

LilMissCiara

God that's confusing..! :O

There is a formula in the log tables but that's for when X is on it's own... In this case X (or V) has a K..! :O

KoolAidRelic

It's a perfectly normal tan^-1 integral, albeit tricky to set up.

Multiply by 1/(k/k) and you get:
-1/k * 1/(g/k + v^2) dv

Which is a normal 1/(a^2 + x^2) with a^2 = g/k.

jamesr1775

is projectiles tht bounce likely this year?

Geog ariphic

KoolAidRelic wrote: »

It's a perfectly normal tan^-1 integral, albeit tricky to set up.

Multiply by 1/(k/k) and you get:
-1/k * 1/(g/k + v^2) dv

Which is a normal 1/(a^2 + x^2) with a^2 = g/k.

While i try to figure that out - do you mean multiply above and below by 1/(k/k), or multiply both sides by it?

Edit:Ok right its a different way of multiplying by k above and below, gotcha.
If that's your definition of a perfectly normal integral, i hate to see what u consider difficult

is projectiles tht bounce likely this year?

came up in my pre, which means they think it will...

KoolAidRelic

Geog ariphic wrote: »

While i try to figure that out - do you mean multiply above and below by 1/(k/k), or multiply both sides by it?

Edit:Ok right its a different way of multiplying by k above and below, gotcha.
If that's your definition of a perfectly normal integral, i hate to see what u consider difficult

Yeah, it's the same as mutiplying by k/k, but just to make it clearer that you don't have a k on the top line. Once you get to that stage though it's a normal one.

The ones I hate are the 1/(a^2 - x^2)

Geog ariphic

jamesr1775 wrote: »

is projectiles tht bounce likely this year?

em sorry again, followed all ur instuctions, its working out well just can't get to the second last line on the marking scheme, i have:

(1/((kg)^(1/2)))*invtan((3kg)^(1/2)) = pi/3

jamesr1775

KoolAidRelic wrote: »

Yeah, it's the same as mutiplying by k/k, but just to make it clearer that you don't have a k on the top line. Once you get to that stage though it's a normal one.

The ones I hate are the 1/(a^2 - x^2)

the one i hate is find the area of a disc WITHOUT THE ****ING HINT!!!
lol sry still pissed about tht

KoolAidRelic

Geog ariphic wrote: »

em sorry again, followed all ur instuctions, its working out well just can't get to the second last line on the marking scheme, i have:

(1/((kg)^(1/2)))*invtan((3kg)^(1/2)) = pi/3

I think you just did your factoring wrong, should be arctan(sqrt(3)).
Here's how I did it: http://i51.tinypic.com/2a813jm.png

aranciata

for the part B of the collisions question... it's usually the i value that's ever involved in the calculations, right?

larkin1993

aranciata wrote: »

for the part B of the collisions question... it's usually the i value that's ever involved in the calculations, right?

yeah

Geog ariphic

KoolAidRelic wrote: »

I think you just did your factoring wrong, should be arctan(sqrt(3)).
Here's how I did it: http://i51.tinypic.com/2a813jm.png

I see where i went wrong, i got it. You're a legend, thank you.

Ps you should have a minus up the very top, which then cancels with the one on ur third line, but we won't fight over it ;P

KoolAidRelic

Geog ariphic wrote: »

I see where i went wrong, i got it. You're a legend, thank you.

Ps you should have a minus up the very top, which then cancels with the one on ur third line, but we won't fight over it ;P

Ah so I should! I was wondering why in my written out ones I had -pi/3 on the other side. It disappears when you square anyway so it doesn't matter.

yannfann

The next hour and a half will see me cram more than I have in the entire year. Cmooooon b2!!!!!! Anyone else not need It for points and tempted to not show up? Or am I the only idiot here? :P