LC Applied Maths 2014 - Before and after discussion

Daniel2590 · 19-06-2014 7:42pm

otpmb wrote: »

Oh, if you break forces up into horizontal and vertical components in q4 on your diagram make sure you do it in different colours (i.e the force in one colour and its' components in another colour) otherwise it's treated as a mistake because you've got the same force in twice. I know this because my teacher corrects the papers every year, and he warned us that loads of people lose marks over this.

Or you can draw a broken line if you want I'm fairly sure

WoolyAbyss · 19-06-2014 8:39pm

Does anyone know if projectiles on an inclined plane is on the ordinary course?

TheBegotten · 19-06-2014 8:45pm

Hands up who's going to have a nervous breakdown if Q5 is the same as last year? Just me? Seriously though, they've been adding different approaches to the standard questions in the last few years. Wedges are overdue, an overtaking question for 1b is due, a U-tube question for 9 is probably due as well. Don't take anything for granted and be prepared to deviate from the usual methods and think on your feet.

Nicke011 · 19-06-2014 9:11pm

I don't know if I'm tired or what, but I feel like I forgot everything and that I'm going to fail

I'm looking at the questions in my folder and I can't understand them

AtomicKoala · 19-06-2014 9:15pm

TheBegotten wrote: »

be prepared to deviate from the usual methods and think on your feet.

Oh god no

Ompala · 19-06-2014 9:22pm

TheBegotten wrote: »

Hands up who's going to have a nervous breakdown if Q5 is the same as last year? Just me? Seriously though, they've been adding different approaches to the standard questions in the last few years. Wedges are overdue, an overtaking question for 1b is due, a U-tube question for 9 is probably due as well. Don't take anything for granted and be prepared to deviate from the usual methods and think on your feet.

AtomicKoala wrote: »

Oh god no

In fairness the stuff you listed there isn't the worst in the world either, U-Tube questions are nice, I was hoping one would appear on my exam

Don't panic in the exam anyways lads, if you stay calm you will be able to pick up majority of the marks by completing your method

TheBegotten · 19-06-2014 9:37pm

Also, I've forgotten to post this incredibly valuable piece of advice/motivation. Good luck! http://www.smbc-comics.com/?id=3011

otpmb · 19-06-2014 9:52pm

Daniel2590 wrote: »

Or you can draw a broken line if you want I'm fairly sure

oh yeah that's fine too you just have to differentiate between the force and its components.

PhysicsKid99 · 20-06-2014 12:25pm

Anyone get k=15?

c0unterpart · 20-06-2014 12:28pm

didnt like that at all.No chance of an A now but sure.

how the hell do you prove tanA < tan B ?

PhysicsKid99 · 20-06-2014 12:32pm

c0unterpart wrote: »

didnt like that at all.No chance of an A now but sure.

how the hell do you prove tanA < tan B ?

I said vx>0 at range, so then I ended up getting 1>0 and then TanA< TanB. It made sense when I did it out...

Ompala · 20-06-2014 12:32pm

And now the wait for SEC to upload the paper is on...

RedSeven7 · 20-06-2014 12:35pm

c0unterpart wrote: »

didnt like that at all.No chance of an A now but sure.

how the hell do you prove tanA < tan B ?

Haven't a clue!

I thought that paper was really tough

Peregrine · 20-06-2014 12:35pm

I even screwed up the pulley question.

TimeToShine · 20-06-2014 12:38pm

What time will the paper be up?

Wouldn't mind a look for old times sake

Peregrine · 20-06-2014 12:39pm

TimeToShine wrote: »

What time will the paper be up?

Wouldn't mind a look for old times sake

Around 5 or 6pm. I could take a picture of some questions when I get home if you want.

Delightfully Bright · 20-06-2014 12:39pm

Everyone I was talking to said it was a tough paper. I'd say they'll be nice in the marking scheme or else applied maths might lose its huge A1 rate.

FHB · 20-06-2014 12:40pm

At least other people found it tough too...

Solid_Shepard · 20-06-2014 12:42pm

To say that was terrible would be an understatement.

Question 1 was alright. The b part was fairly easy, but I couldn't get (ii) as I forgot what to do.

Question 2 was...less alright. The a part was absolutely terrible, to say the least; I can't remember a single time something like that came up. The b part was fine.

Question 3 was ok. The a part was tricky and really time-consuming, while the b part was ok. The (ii) was very tricky, I thought, and I was forced to move on past it due to the time.

Question 4 was...well...I don't like that diagram so didn't do it. It looks very tricky. The b part seems alright.

Question 5 wasn't too bad in terms of maths, but finding the co-efficient of restitution took so long that there was ample room to slip-up, and I ended up making an error in the maths which had a knock on effect.

Question 6 I didn't like. The first part was a tricky way for them to ask to prove Simple Harmonic Motion. I ended up making an error looking at it now though, as I used the "four" instead of "one over four" which was a stupid error. This had a knock on effect on the second part. The b part I didn't like either. The first part was kind of ok, but I only just noticed that I completely misread the (ii) so that went terribly too.

Question ten seemed ok. I'm worried that I thought it went ok.

Overall, I had been expecting an A1; now, I am not.

EDIT: Ok, so under the absolutely worst case scenario, where each part is 25 marks, an i part is 15, and an ii part is ten, and they remove all of the marks for an incorrect answer, I would be down to 235/300. I don't think it'll be marked that harshly, so maybe I got a B1 pushing it which is better than I thought. I'm not hopeful though.

PhysicsKid99 · 20-06-2014 12:45pm

K=15 anyone?

TimeToShine · 20-06-2014 12:46pm

Nimrod 7 wrote: »

Around 5 or 6pm. I could take a picture of some questions when I get home if you want.

Ah it's alright i'll wait around for it. The physics paper looked lovely so I was wondering would this one be a walk in the park as well - apparently not!

jimbob95 · 20-06-2014 12:47pm

Anyone else feel like they will be lucky to pass after feeling beforehand like they would get at least a B?

Delightfully Bright · 20-06-2014 12:49pm

jimbob95 wrote: »

Anyone else feel like they will be lucky to pass after feeling beforehand like they would get at least a B?

I haven't heard of anyone yet who liked the paper so don't give up yet. They'll throw attempt marks at us to keep the high A rate.

MegGustaa · 20-06-2014 12:49pm

RedSeven7 wrote: »

Haven't a clue!
I thought that paper was really tough

I used the expression for Tan A from the first part (which was in terms of Tan

and put it < Tan B and went from there, ended up with a line like Tan B > 0 which is true if B is an acute angle, which I guess it has to be.

Very rough paper. Was hoping for an A1, now I'll be lucky to get a B1/B2. Oh well. Didn't need Applied Maths for points, realistically I was only doing it to get a head start on mechanics for 3rd level.

AtomicKoala · 20-06-2014 1:00pm

Well there goes my A

c0unterpart · 20-06-2014 1:04pm

AtomicKoala wrote: »

Well there goes my A

same.

HIGH FIVE !

Peregrine · 20-06-2014 1:08pm

TimeToShine wrote: »

Ah it's alright i'll wait around for it. The physics paper looked lovely so I was wondering would this one be a walk in the park as well - apparently not!

.

Shanrahan · 20-06-2014 1:42pm

I got k=32?...

Ompala · 20-06-2014 1:48pm

For Q 9
(a) 3200 and 4800 kg/m^3
(b) (i) x = 45.18 cm (or to be exact, x^2 = 100,000/49)
(ii) Tension = 160 N
(iii) Density = 428.157 kg/m^3 ( or 3000/7 kg/m^3)

RedSeven7 · 20-06-2014 1:49pm

For Question 4(a) - the pulley - does anyone know if the acceleration of A and B is the same, or if the acceleration of B a multiple of the acceleration of A or vice versa??

Nicke011 · 20-06-2014 1:52pm

Shanrahan · 20-06-2014 1:54pm

RedSeven7 wrote: »

For Question 4(a) - the pulley - does anyone know if the acceleration of A and B is the same, or if the acceleration of B a multiple of the acceleration of A or vice versa??

Yeah they should be the same and then force equals mass times acceleration

Nicke011 · 20-06-2014 1:58pm

RedSeven7 wrote: »

For Question 4(a) - the pulley - does anyone know if the acceleration of A and B is the same, or if the acceleration of B a multiple of the acceleration of A or vice versa??

Shanrahan wrote: »

Yeah they should be the same and then force equals mass times acceleration

I think it's all one acceleration a... And I used T for all tensions throughout the string cause it's only one string.

PhysicsKid99 · 20-06-2014 2:16pm

Nicke011 wrote: »

I think it's all one acceleration a... And I used T for all tensions throughout the string cause it's only one string.

I used a and 2a because A had two strings attached... Oops

MegGustaa · 20-06-2014 2:24pm

PhysicsKid99 wrote: »

I used a and 2a because A had two strings attached... Oops

I had the accln of B was half that of A because when A moves forward, the length of the string string both gets longer and shorter because of the way it's set up, so B only moves up half the distance that A moves forwards. Don't really know what I was thinking tbh.

qweerty · 20-06-2014 2:30pm

The hanging-block's acceleration is twice that of the other...unless this sun is doing weird things to my head. If I'm wrong, you won't notice I'm blushing cause this sun is doing weird things to my face.

matthew8 · 20-06-2014 2:41pm

That was a tough paper and pretty out there. Still, apart from question 5 (b) I think I got the answers. Questions 2 and 10 were nice, and though 3 had some trig manipulation, it was fairly basic stuff otherwise. To prove tan B > tan a here's how:

(1+2tan*2B) (tan a) = tan B (taking the bottom off the right hand side and multiplying it by the left.

Therefore if 1+2tan*2B is greater than 1 tan B is greater than tan a (because multipling it by more than one means you get a bigger number).

To prove: 1+2tan*2B>1
2tan*2B>0
tan*2B>0
(tanB)*2>0 true because (real)*2 > 0.

Nicke011 · 20-06-2014 2:46pm

qweerty wrote: »

The hanging-block's acceleration is twice that of the other...unless this sun is doing weird things to my head. If I'm wrong, you won't notice I'm blushing cause this sun is doing weird things to my face.

I actually think you're right...
Fu*k it anyway

matthew8 wrote: »

That was a tough paper and pretty out there. Still, apart from question 5 (b) I think I got the answers. Questions 2 and 10 were nice, and though 3 had some trig manipulation, it was fairly basic stuff otherwise. To prove tan B > tan a here's how:

(1+2tan*2B) (tan a) = tan B (taking the bottom off the right hand side and multiplying it by the left.

Therefore if 1+2tan*2B is greater than 1 tan B is greater than tan a (because multipling it by more than one means you get a bigger number).

To prove: 1+2tan*2B>1
2tan*2B>0
tan*2B>0
(tanB)*2>0 true because (real)*2 > 0.

Please tell me are you a student or a teacher? ::D

matthew8 · 20-06-2014 2:54pm

Nicke011 wrote: »

Please tell me are you a student or a teacher? ::D

Student.

For 4 part a indeed the acceleration of A is half acceleration B, got that one wrong but the same thing came up in 2008 and checked it just there.

Anyone get the answer to 4 b part ii, I got 2.67 and 17.47 but no idea if it's right.

MegGustaa · 20-06-2014 3:24pm

qweerty wrote: »

The hanging-block's acceleration is twice that of the other...unless this sun is doing weird things to my head. If I'm wrong, you won't notice I'm blushing cause this sun is doing weird things to my face.

That actually makes so much sense. Damn. Oh well.

matthew8 · 20-06-2014 3:34pm

Other answers I got:
1a i 24 -.5t*2
ii 18.375

b i : .53
ii: 23.74

2a ii 18:51
b ii 91

3a something like 12

5a ii .84mu*2
bi (pretty sure it's wrong) .77

10 a i 4.22
ii .33

b i 1 and 2 seconds
ii t*3 over 3+3t*2 over 2+2t+1
iii 1 metre (could be wrong)

MegGustaa · 20-06-2014 3:37pm

matthew8 wrote: »

Other answers I got:
1a i 24 -.5t*2
ii 18.375

b i : .53
ii: 23.74

2a ii 18:51
b ii 91

3a something like 12

5a ii .84mu*2
bi (pretty sure it's wrong) .77

10 a i 4.22
ii .33

b i 1 and 2 seconds
ii t*3 over 3+3t*2 over 2+2t+1
iii 1 metre (could be wrong)

I don't remember what I got for the other Qs but I got exactly the same for Q1a and Q10

a bit of a relief!

Ompala · 20-06-2014 3:53pm

Q3 (a) I think its u = 4.9sqrt33 (or u = 28.148)
Q10 a (i) v1 = 4.2248 m/s (ii) s = 0.330997 m
b (i) Changes at 1 and 2 seconds (ii) s = (t^3)/3 - (3t^2)/2 + 2t + 1 (iii) 2/3 m

matthew8 wrote: »

Student.

For 4 part a indeed the acceleration of A is half acceleration B, got that one wrong but the same thing came up in 2008 and checked it just there.

Anyone get the answer to 4 b part ii, I got 2.67 and 17.47 but no idea if it's right.

I got t = 0.267s and x = 14.5 cm, i don't think you converted from cm to m

Then again I could be wrong too!

matthew8 · 20-06-2014 4:03pm

Ompala wrote: »

Q3 (a) I think its u = 4.9sqrt33 (or u = 28.148)
Q10 a (i) v1 = 4.2248 m/s (ii) s = 0.330997 m
b (i) Changes at 1 and 2 seconds (ii) s = (t^3)/3 - (3t^2)/2 + 2t + 1 (iii) 2/3 m

I think you've made a mistake on 10 b iii, integrating it like it was only one curve, but it was like a curve that went over and under so you had to do it for the first and the second second separately, which checks out because I got 1/6 metres for the second second, in case you didn't already know (I made a mistake too here, my answer on this threadis a correction on it).

Just redid 3a and yeah that's the answer I got, not around 22.

Sorry for all the post mortem lads, I can't help myself.

Ompala wrote: »

I got t = 0.267s and x = 14.5 cm, i don't think you converted from cm to m

Then again I could be wrong too!

The cm really caught me off guard there and I never dealt with it, but surely then my answer should be 100 times your answer?

Anyway it should only be a blunder for me.

Ompala · 20-06-2014 4:18pm

matthew8 wrote: »

I think you've made a mistake on 10 b iii, integrating it like it was only one curve, but it was like a curve that went over and under so you had to do it for the first and the second second separately, which checks out because I got 1/6 metres for the second second, in case you didn't already know (I made a mistake too here, my answer on this threadis a correction on it).

Just redid 3a and yeah that's the answer I got, not around 22.

Sorry for all the post mortem lads, I can't help myself.

matthew8 wrote: »

The cm really caught me off guard there and I never dealt with it, but surely then my answer should be 100 times your answer?

Anyway it should only be a blunder for me.

Well spotted on Q10, annoyed at myself for missing that. But your answer makes sense though, as you are changing direction at 2 and 1 seconds (in my head anyway)

Q3 was very strange, took me a while to cop it.

Not 100 times as we had to take the square root, so thats why its off by 10 not 100

PhysicsKid99 · 20-06-2014 4:37pm

T=0 and t= 3, anyone? I just said it changes when v=0 and integrated

matthew8 · 20-06-2014 4:38pm

Ompala wrote: »

Well spotted on Q10, annoyed at myself for missing that. But your answer makes sense though, as you are changing direction at 2 and 1 seconds (in my head anyway)

Q3 was very strange, took me a while to cop it.

Not 100 times as we had to take the square root, so thats why its off by 10 not 100

Good stuff, works out there I checked it. Anything for question 5? that's the only thing left in the post mortem really. Can't believe I messed up the 2 questions I find easiest usually, but the good news if they give you nearly all the marks for the equations in 4, and getting v1 and v2 in Q5, even though the lion's share of the time is spent doing the hard graft afterwards. As for the difference in the value of x in q4, did you take the acceleration of the wedge into account for the relative acceleration? Were we supposed to?

matthew8 · 20-06-2014 4:40pm

PhysicsKid99 wrote: »

T=0 and t= 3, anyone? I just said it changes when v=0 and integrated

Did you take into account that starting velocity was 2? That's where you would've gone wrong to get those. In fact I'm sure, because if you didn't your equation would have been t*2 -3t, which gives 0 and 3.

PhysicsKid99 · 20-06-2014 4:48pm

matthew8 wrote: »

Did you take into account that starting velocity was 2? That's where you would've gone wrong to get those. In fact I'm sure, because if you didn't your equation would have been t*2 -3t, which gives 0 and 3.

Well, oops. I didn't think of that. Thanks, though

How many marks would I lose, do you think?

matthew8 · 20-06-2014 4:51pm

PhysicsKid99 wrote: »

Well, oops. I didn't think of that. Thanks, though How many marks would I lose, do you think?

You'd definitely be down 3, and if they think it oversimplifies the question you'd be down 6 but I think that's a harsh interpretation.

** LC Applied Maths 2014 - Before and after discussion **

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LC Applied Maths 2014 - Before and after discussion