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

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 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.

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

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 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.

matthew8 wrote: »

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?

I got the same answers for Q1 too btw
Really getting nowhere with Q5, got 0.875mu^2 for part a, for part b did you have to solve a quadratic for it?
I did account for relative acceleration of wedge in Q4, my reasoning being its like the "net" acceleration of the block. I could be wrong though.

PhysicsKid99 wrote: »

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...

From part i, if you got it, you took tana to equal tanB over 1+2tan^2B. If you can prove that all that is less than tanB, you've proved tana is less than tan B

Welp. I bottled that. At least I got my Wedge out!

Ompala wrote: »

I got the same answers for Q1 too btw
Really getting nowhere with Q5, got 0.875mu^2 for part a, for part b did you have to solve a quadratic for it?
I did account for relative acceleration of wedge in Q4, my reasoning being its like the "net" acceleration of the block. I could be wrong though.

Strange that we got different answers then (did you split up the wedge acceleration into the 2 diagonals?), mine was wrong for Q5 I checked but I think you might be wrong too. The second part lead to a quadratic, just checked there and made an error with my plus and minus signs. It's just the most annoying thing when you feel under pressure for time and you come up with an error like that and it ends up costing you more time.

matthew8 wrote: »

Strange that we got different answers then (did you split up the wedge acceleration into the 2 diagonals?), mine was wrong for Q5 I checked but I think you might be wrong too. The second part lead to a quadratic, just checked there and made an error with my plus and minus signs. It's just the most annoying thing when you feel under pressure for time and you come up with an error like that and it ends up costing you more time.

Hmm that rings a bell about diagonals, but its been nearly a year since I did App Maths (going through last years paper on this actually) its gone out of my head.

Did not like Q5. Someone else might be able to come along and solve it, but I'm out!

Once again those who studied hydrostatics benefitted massively, it was a very straightforward question, much simpler than many of the others.

You seem to have done very well though in the paper so I wouldn't worry, I'd say you got an A1.

Ompala wrote: »

Feck that Q5 anyways!
I did the number crunching for the quadratics and explored the possibilities but if you go through all the combinations you get e = sqrt46/14 = 0.48
Getting k from the second part poses problems as you get two different answers depending on which solutions you use from the quadratic, I got k = 6.93 or k = 2.41.
Lads I'm totally baffled by this question

I got the 0.48, didn't get k. Im hoping that not getting k but getting the rest of the q will get me 40 marks

Any answers for 1 out there?

Did anyone find q8 suspiciously easy?

mcratsix wrote: »

Did anyone find q8 suspiciously easy?

Yup, I think so. What did you get for k? I got 15

PhysicsKid99 wrote: »

I think that I just cried of happiness...

I'm glad, cos thats the first bit of good news coming from this thread all day!