Physics Aftermath

eZe^

sean_keevey wrote:

Sorry i had assumed that the ammeter was already directly 'beside' the diode. My mind is a bit of a mush...just coverered 75% of the chemistry course. Physics is a distant memory.

/edit wait I just looked at the question, it is not specified where the ammeter is when the diode is forward biassed. In theory it should be in the exact same place as when the diode is reversed, ie beside the Diode

Oh, you were talking about forward bias?!?! In that case the voltmeter doesnt connect to the ammeter at all, it only measures the p.d between the diode.

Kwekubo

eZe^ wrote:

I put the piece of copper (connected to joulemeter) in a boiling tube of glycerol and heated it with a joulemeter... Found the final temperature and reading on joulemeter and then removed it from glycerol and added to the calorimeter... Seemed ok to me!

I just said I stuck it in a water bath until the temperature got to 100 celsius - opinions?

rjt

Mushy wrote:

Q11: My favourite! The little article...never looked at it. Still just so damn easy. Full marks here. 56/56

How'd you get 11(b) without reading the text? :P (and congratulations on the A).

Edit: n/m, I just saw 'ordinary level', sorry :P

When I first opened the paper, I thought "yes!" (in fact half of the exam hall made various approving noises). This lasted until we all looked at section B and/or question 2 (we all did the experiment the other way, had no idea about this method).

Luckily, there were just enough questions to get me through - I thought 5,7,9 and 12 were all do-able, and I think I should've managed an A.

Feddd

Kwekubo wrote:

I just said I stuck it in a water bath until the temperature got to 100 celsius - opinions?

I based it on the experiment to find the Shc of copper. Drew the diagram and said that its heated by the coil+glycerol in one hole and temp recorded by the thermometer +glycerol in the other hole.
Think that sounds ok? Didn't mention boiling tubes or boiling water like everyone else seemed to.

And in regards the quote: You explained how to heat it but you are also asked how to measure its temperature.

Tomlowe

little copper granules in the bottom of a beaker over a bunsen with a thermometer in... whats wrong with that

Kwekubo

Feddd wrote:

I based it on the experiment to find the Shc of copper. Drew the diagram and said that its heated by the coil+glycerol in one hole and temp recorded by the thermometer +glycerol in the other hole.
Think that sounds ok? Didn't mention boiling tubes or boiling water like everyone else seemed to.

And in regards the quote: You explained how to heat it but you are also asked how to measure its temperature.

Oh, well I said that too - thermometer. Everyone seems to have reacted differently to this in the heat of the moment!

Feddd

Kwekubo wrote:

Oh, well I said that too - thermometer. Everyone seems to have reacted differently to this in the heat of the moment!

Impressive pun, possibly referring to Q1 as well as Q2.

Gangsta

ZorbaTehZ wrote:

@Gangsta: Amplitude is the distance between the maximum displacement and the point of equilibrium, so by that logic it must be at 285mm - why do you think it could be 280mm? (so I can follow your train of thought)

oh sh!t, sorry dude I meant to say the pt of equilibrium is 285mm:o my bad.

Feddd

Question: Wasn't very familiar with Q4 as I hate electricity, but instead of having a poteniometer in the circuit I had a variable resistor and said that potential difference is altered by altering the resistor. Will I still get the marks do ye think?

JC 2K3

Yup.

As long as it's a source of varable voltage and is connected right you're grand.

adam_ccfc

I'm doing a rough addition of my marks and it is going to be pretty close for me!

Couple of very silly mistakes. I'll be in the range of about 88-94% somewhere.

amacachi

physics for me was the same as the rest of my subjects so far, its not that it was really hard, it was just awkward and the way the questions were put together really didnt maximise my marks. no-one to blame but meself tho

JC 2K3

adam_ccfc wrote:

I'm doing a rough addition of my marks and it is going to be pretty close for me!

Couple of very silly mistakes. I'll be in the range of about 88-94% somewhere.

Same here, I reckon I could dip to a B1, but if the marking scheme isn't strict I could be in A1 land.

Feddd

JC 2K3 wrote:

Same here, I reckon I could dip to a B1, but if the marking scheme isn't strict I could be in A1 land.

Exact same for me. I made 2 extremly retarded mistakes. In the theme question I completly missed the "Watts" in 300 giga watts and took it as 300giga watts a year, and in the mechanics question I took 315mm as the maximum displacement instead of 25mm which was the extention and also got the third part of that wrong cause I wasn't concentrating enough.

Made some more mistakes but they were genuine mistakes. The above ones are just silly slips which I should have known but wasn't focused enough and may cost me the A.

timmywex

http://www.examinations.ie/index.php?l=en&mc=en&sc=ep&formAction=subject


http://www.examinations.ie/archive/exampapers/2007/LC021ALP000EV.pdf


a link to the different papers...

Feddd

By the way, whats the policy in physics on carrying on mistakes? I know its usually 3 marks per line in a calculation, but if I put in a wrong number 1) Do I lose all 3 marks for that line where I substituted my values or just 1 or 2 if there were a few values to substitute? and 2) If I calculate the wrong numbers correctly do I get the marks after that line?(Usually 2 for calculation of the final line).
Someone please enlighten me because if its true then I may have gotten the A1 and I will be once again motivated to study for my remaining subjects!

E92

I think its like Maths, the same error in the same section is only penalised once ie, wherever you make the mistake you lose themarks there, but if get the 'right' answer ie you keep going with the wroing figures and work it out as best you can you'll get the rest of the marks.


I thought that paper was horrible, Q2 is too specific, as was mentioned by someone else here look at page 29 of the syllabus, and you'll se why, same goes for Q3, you dont jhave to do that experiment with a Graph, I spoke to people in my year who never did that experiment with a Graph(its not mandatory), we were lucky that our Physics teacher who finished the couse with us way back in November told us how to deal with the Graph if they asked it, Q6 was an Applied Maths question, very doable if you do that section of Applied Maths, but it muust habve been awful for everyone else. I actually thought it looked impossible at first(Q6), but then I looked again and realised that it was an Applied Maths kind of Question and that along with Q12 part a), which was also an Applied Maths type of Question(though a much easier Question than 6) saved my arse in Physics yesterday.

I dont really like Post Mortems too much, but does anyone know the answer to Q1 part ii) and iii), or more specifically, how they worked out the answer? I'm just curious as to what people did, cause mine didnt equal(you should get the same answer for both parts, shouldn't you), and I'd like to know where I went wrong.

carlowboy

E92 wrote:

I think its like Maths, the same error in the same section is only penalised once ie, wherever you make the mistake you lose themarks there, but if get the 'right' answer ie you keep going with the wroing figures and work it out as best you can you'll get the rest of the marks.


I thought that paper was horrible, Q2 is too specific, as was mentioned by someone else here look at page 29 of the syllabus, and you'll se why, same goes for Q3, you dont jhave to do that experiment with a Graph, I spoke to people in my year who never did that experiment with a Graph(its not mandatory), we were lucky that our Physics teacher who finished the couse with us way back in November told us how to deal with the Graph if they asked it, Q6 was an Applied Maths question, very doable if you do that section of Applied Maths, but it muust habve been awful for everyone else. I actually thought it looked impossible at first(Q6), but then I looked again and realised that it was an Applied Maths kind of Question and that along with Q12 part a), which was also an Applied Maths type of Question(though a much easier Question than 6) saved my arse in Physics yesterday.

I dont really like Post Mortems too much, but does anyone know the answer to Q1 part ii) and iii), or more specifically, how they worked out the answer? I'm just curious as to what people did, cause mine didnt equal(you should get the same answer for both parts, shouldn't you), and I'd like to know where I went wrong.

Agreeing with you apart from Q6. I don't do Applied Maths (was crap at it as I didn't put any effort in). If you knew omega^2=k/m, it was the easiest question on the paper.

adam_ccfc

I don't do applied maths, but I knew how to work that problem, so I was alright.

Feddd

E92 wrote:

I dont really like Post Mortems too much, but does anyone know the answer to Q1 part ii) and iii), or more specifically, how they worked out the answer? I'm just curious as to what people did, cause mine didnt equal(you should get the same answer for both parts, shouldn't you), and I'd like to know where I went wrong.

They came out perfectly equal for me and my friends.
You may have left out the weight of the meter stick? Only thing I can think of. I left it out aswell at first but when I was finished the exam and looking over it I relised it.

I do applied maths but don't cover the section that came up in Q6 but considering hookes hasn't come up in years I studied it well the night before and got lucky. I agree that it was applied mathsy considering there were so many marks for calculations. Made a few mistakes in it but hopfully wil be amrked easy as its probably the hardest part of the mechanics course.

Q12(a) was an absolute walkover for applied maths students though.

E92

I tried it with the moments being about the 0 cm mark of the metre stick, it was even more wrong than when I ignored the weight of the metre stick.

Then I tried it the the moments being about the 50.4 cm mark of the metre stick, and since its about there the weight of the metre stck can be ignored.

E92

carlowboy wrote:

Agreeing with you apart from Q6. I don't do Applied Maths (was crap at it as I didn't put any effort in). If you knew omega^2=k/m, it was the easiest question on the paper.

Oh I thought 6 was a lovely question, as I said it saved my ass yesterday, I found it easy, but it was strange to see something so like Applied Maths on it. We only spent about a day or 2 in Physics on SHM, we spent over month on it in Applied Maths.

SuZyQ!

i thought the paper was really challenging and there was a few little bits that threw me off but I think I did weel Im hopping for a good solid B please god

lemansky

If you learn physics out of the book it was a hard paper because you had to apply knowledge more than is usual in physics,so it appeared harder than other years.But if you understand physics it was handy.

eZe^

lemansky wrote:

If you learn physics out of the book it was a hard paper because you had to apply knowledge more than is usual in physics,so it appeared harder than other years.But if you understand physics it was handy.

It also caught students out who only studied particular sections, mar shampla the emission spectrum question in the doppler effect section.

JC 2K3

E92 wrote:

I dont really like Post Mortems too much, but does anyone know the answer to Q1 part ii) and iii), or more specifically, how they worked out the answer? I'm just curious as to what people did, cause mine didnt equal(you should get the same answer for both parts, shouldn't you), and I'd like to know where I went wrong.

I got a difference of about 1 between them and said it verified the laws of equilibrium within experimental error.

lemansky

eZe^ wrote:

It also caught students out who only studied particular sections, mar shampla the emission spectrum question in the doppler effect section.

Exactly.They like mixing their sections together,even if it is only in small things like the silicon as a semiconductor question thrown into a heap of questions that were at odds with that one.
I suppose its another lesson that has to be learned for next year's leaving.You can't afford to leave things out.

lemansky

JC 2K3 wrote:

I got a difference of about 1 between them and said it verified the laws of equilibrium within experimental error.

After numerous attempts they eventually worked out equal for me.I kept leaving things out or hitting the wrong buttons on the calculator.Did you run the figures a few times and get one as the difference each time?

adam_ccfc

The clockwise and anticlockwise moments were exactly equal, as were the upward and downward forces.

Thomas_S_Hunterson

lemansky wrote:

After numerous attempts they eventually worked out equal for me.I kept leaving things out or hitting the wrong buttons on the calculator.Did you run the figures a few times and get one as the difference each time?

They worked out exactly equal for me too.

JC 2K3

Nah, I did it once and noticed I was running out of time.

I doubt a miscalculation warrants more than one lost mark though tbh.

I reckon I might have taken 50 as the mid point when working out the distance of one or two forces or something.

ZorbaTehZ

adam_ccfc wrote:

The clockwise and anticlockwise moments were exactly equal, as were the upward and downward forces.

Same for me.

lemansky

JC 2K3 wrote:

Nah, I did it once and noticed I was running out of time.

I doubt a miscalculation warrants more than one lost mark though tbh.

I reckon I might have taken 50 as the mid point when working out the distance of one or two forces or something.

Exactly.Its only a miscalculation not a case of not knowing what to do.Easy mistake to make as well.Thats what I did one of the times.

ZorbaTehZ

JC 2K3 wrote:

I got a difference of about 1 between them and said it verified the laws of equilibrium within experimental error.

1 Newton ... thats quite a big difference tbh.

JC 2K3

1 Newton centimetre

ZorbaTehZ

JC 2K3 wrote:

1 Newton centimetre

Iirc my answers went to two places of decimal, and still matched up number for number ... so even 1 Ncm is a lot tbh ... usually when it's diliberately not equal its usually, by 0.01 or something.

JC 2K3

Well if it was N m, the SI units, it would have been 0.01.....

But meh, not worth discussing really. I've lost one or two marks tops.

adam_ccfc

Just a quicky, in the Hooke's Law question, when it asked you to derive an equation that relates the acceleration to the displacement, I assume they just wanted you to turn F=-ks into a=(-w^2)(s) ?

Nehpets

adam_ccfc wrote:

Just a quicky, in the Hooke's Law question, when it asked you to derive an equation that relates the acceleration to the displacement, I assume they just wanted you to turn F=-ks into a=(-w^2)(s) ?

Yep, I think so. That's what I did

cocoa

adam_ccfc wrote:

Just a quicky, in the Hooke's Law question, when it asked you to derive an equation that relates the acceleration to the displacement, I assume they just wanted you to turn F=-ks into a=(-w^2)(s) ?

*shrug* they might have meant that, I assumed they meant adding the forces (gravity down, the elasticity up) and it kindah cancles out so that you're left with - a number by s.

Roonels

lemansky wrote:

If you learn physics out of the book it was a hard paper because you had to apply knowledge more than is usual in physics,so it appeared harder than other years.But if you understand physics it was handy.

well said i agree wholeheartedly. the previous few years have enabled you to spit answers onto the page, this year it turned out to be a bit different due to thought aspect.

adam_ccfc

cocoa wrote:

*shrug* they might have meant that, I assumed they meant adding the forces (gravity down, the elasticity up) and it kindah cancles out so that you're left with - a number by s.

I did that, but then I thought about it and crossed it out. Poorly worded, I thought.