* Physics HL 2011 * HL predictions / discussion / aftermath * (1 thread only please)

augmented reality

Oh, now I see, thanks!

DM360

augmented reality wrote: »

I'm just doing an experiment question now from my mocks, it's measuring the speed of sound in air with the glass tube.
They give values for frequency and length and ask to draw a graph, then to calculate the speed of sound in air using the graph.

Do I need to change anything first before plotting??
How do you calculate the speed using the graph??
Really think something like this will come up.
Thanks!

Someone gave a solution with wavelength but it most likely gives you length of the column (l)

y-axis = length (m)
x-axis = 1/frequency (Hz^-1)

slope*4 = speed of sound in air

However the end correction (the 0.3d) isn't accounted for

luciemc

Does anyone think Rutherford could come up? It's the 100th anniversary of his alpha particle/gold foil experiment? ..might be too easy, there anything difficult they could ask?

Floydy B

LimboPanto wrote: »

I'm feeling way in over my head with Higher Physics. Got a D1 in the mocks, really did my best to put the work in since then, but with all the other subjects and exams, I've sort of let it slip for the past two weeks. It's a bit late now to attempt to go through the whole textbook, and I'm at a total loss as to how I should make use of the three days I have before the exam. Any tips, advice, help out there? Thanks in advance =]

You've got two days.so just use them well. I got a D2 in the mocks,mostly because all i studied was experiments,same as you I've put in the work since then,but i still have a load of work to do for the weekend. Just make sure you can do all the question 5's from every year and that alone should really stand to you,they cover so much. We did partical physics for the option,easy enough to learn. Q. 12's are generally nice enough too. Learn as many diagrams as you can then for the small experiments to show various principles,and you can generally work out the rest from them. Other then that,just hope that it will be a sweet paper! This may be stuff you know already,but this is just the approach i'm taking!

The_Don_21

I'm just gonna watch the Back to the Future Trilogy and hope for the best guaranteed at least an A2 i reckon..

Geog ariphic

Wats_in_a_name wrote: »

Apparently conservation of momentum is likely to come up as well as measurement of speed of sound in air.

Yes! So i've heard, from two physics teachers in my school. That exp. on speed of sound hasnt been up for a while though, that's the basis for this.

What's everyone thinking for cicular motion, deriving the gravtational formula etc? Likely?

Geog ariphic

LilMissCiara wrote: »

The constants are in the log tables but the variables will be at the end of the question!

A guy in my class knows a man who actually corrects the physics papers. Sweet right? He said now they WILL NO LONGER ACCEPT FORMULAE FOR DEFINITIONS, even when you write down what every symbol means after it.

But fear not! There are two solutions.

1)I'd reccomend this http://www.thephysicsteacher.ie/leavingcertphysicsrevision.html and click on the word file for definitions.
It does out a list of the VAST majority of definitions that are on the course. (You'll need to do a little editing to print out however, its very spread out).

2)Should you forget a particular definition in the exam, 'derive' the worded definition by finding the relevant formula and filling in the words for their letters, then seeing how you could write as a sentence.

Eg: g= (G(m1)(m2))/(d^2)
= (G(one mass)(other mass))/(square of distance between the two)
= "The product of two point masses, divided by the distance between the two points"

Obviously this will only take you so far and you need some idea of the def. before starting, but it will get you off to a good start.

Hope this helped.:)

LilMissCiara

Geog ariphic wrote: »

A guy in my class knows a man who actually corrects the physics papers. Sweet right? He said now they WILL NO LONGER ACCEPT FORMULAE FOR DEFINITIONS, even when you write down what every symbol means after it.

But fear not! There are two solutions.

1)I'd reccomend this http://www.thephysicsteacher.ie/LC%20Physics/Revision/3.%20Definitions.doc
it does out a list of the VAST majority of definitions that are on the course. (You'll need to do a little editing to print out however, its very spread out).

2)Should you forget a particular definition in the exam, 'derive' the worded definition by finding the relevant formula and filling in the words for their letters, then seeing how you could write as a sentence.

Eg: g= (G(m1)(m2))/(d^2)
= (G(one mass)(other mass))/(square of distance between the two)
= "The product of two point masses, divided by the distance between the two points"

Obviously this will only take you so far and you need some idea of the def. before starting, but it will get you off to a good start.

Hope this helped.:)

Isn't it obvious you can't put a formula you are given down as an answer..?!

Geog ariphic

Sorry, possibly i wasnt clear.
When they asked for a definition, they used to accept a formula, cos there were hardly any in the Tables. Just so long as you explained what each letter stood for in your equation.
From what my contact says, this is no longer acceptable,
as last year pretty much every definition was given as a formula in the log tables,
so i'm going to brush up on my worded definitions and not risk it.

clartharlear

I'm kinda expecting to see SHM, current in a magnetic field and a wheatstone bridge.

But I wouldn't be putting any money on any predictions! As a physics teacher, I always try to emphasize how much everything is connected.
Being able to make connections and transfer knowledge is quite the big thing in education these days, so if *I* were the examiner, I would be doing my best to mix up the topics in the questions as much as possible.
eg moments on a current carrying conductor in mag field, momentum in radioactive decay.

Basically, keep an open mind in the exam! And be aware that physics can sometimes reward the student who is able to think and work something out, even if they didn't learn it off...

Colm92

Geog ariphic wrote: »

A guy in my class knows a man who actually corrects the physics papers. Sweet right? He said now they WILL NO LONGER ACCEPT FORMULAE FOR DEFINITIONS, even when you write down what every symbol means after it.

But fear not! There are two solutions.

1)I'd reccomend this http://www.thephysicsteacher.ie/LC%20Physics/Revision/3.%20Definitions.doc
it does out a list of the VAST majority of definitions that are on the course. (You'll need to do a little editing to print out however, its very spread out).

2)Should you forget a particular definition in the exam, 'derive' the worded definition by finding the relevant formula and filling in the words for their letters, then seeing how you could write as a sentence.

Eg: g= (G(m1)(m2))/(d^2)
= (G(one mass)(other mass))/(square of distance between the two)
= "The product of two point masses, divided by the distance between the two points"

Obviously this will only take you so far and you need some idea of the def. before starting, but it will get you off to a good start.

Hope this helped.:)

This is in no way true, so dont worry people. Pat Doyle from the institute of education was on the radio today and he said you can use the forumlae and explain all the letters for definitions. So no offence but I'm just going to take his word for it.

clartharlear

Oh yeah, and as a physics teacher, I would really like you to know that nothing makes me happier than a clear, well-labelled diagram.
Especially when the question didn't even specifically ask for a diagram, and yet it's the best way to explain something.

LilMissCiara

Geog ariphic wrote: »

Sorry, possibly i wasnt clear.
When they asked for a definition, they used to accept a formula, cos there were hardly any in the Tables. Just so long as you explained what each letter stood for in your equation.
From what my contact says, this is no longer acceptable,
as last year pretty much every definition was given as a formula in the log tables,
so i'm going to brush up on my worded definitions and not risk it.

No I get what you mean but I thought it would be obvious that because we now get the formulas we can't use them as answers and instead have to use a definition..

LilMissCiara

Colm92 wrote: »

This is in no way true, so dont worry people. Pat Doyle from the institute of education was on the radio today and he said you can use the forumlae and explain all the letters for definitions. So no offence but I'm just going to take his word for it.

It's what we were told as well. I wouldn't risk it.

(It being definition not formula)

stealinhorses

I heard Pat Doyle on the radio saying that explaining the formulae is an acceptable way for answering the definition questions.

And why wouldn't it be?
Instead of saying, for example, "Pressure is defined as force per unit area", if you just wrote P=F/A, where P is pressure, F is force in Newtons and A is area in m^2, then you're stating the exact same information, but expressed mathematically.
It's not like the examiner won't understand the equation :S

DM360

Colm92 wrote: »

This is in no way true, so dont worry people. Pat Doyle from the institute of education was on the radio today and he said you can use the forumlae and explain all the letters for definitions. So no offence but I'm just going to take his word for it.

Absolutely agree, the thing they reckon will happen, Pat Doyle said it himself, is that the constants like electron mass, speed of light etc. won't be on the paper. Instead you'll just have to look them up in the Fundamental Constants page of the tables.

Went to an Easter Institute course with him, fantastic teacher, knows the syllabus and exam papers inside out, I'd have full faith in him

Oh and as a side note to the guy who claims this change, plenty of teachers correct exam papers so a guy in your class knowing one person who corrects the papers is no big deal, there are hundreds of correctors and they would have told their classes

fresh2011

LOL, you were so wrong! Yeah I was at a course with Pat Doyle too and he has in all his notes that you can just give the definition and explain the symbols, so don't panic.

Really hoping the mechanics and electromagnetic induction questions aren't too hard if they appear on the paper

sparagon

What is the distance between a crest and a trough?

RP77

The horizontal distance between crest and next trough is half a wavelength

stealinhorses

Just a quick question about this whole physical constants deal.

If they're not given in the questions this year and, let's say, we have to use the value for the speed of light in an equation. Normally this would be given as 3x10^8 m/s in the question, but in the tables book it's 2.99792458x10^ 8m/s.

Does that mean we always have to use the full value given in the tables book for every question?

DM360

stealinhorses wrote: »

Just a quick question about this whole physical constants deal.

If they're not given in the questions this year and, let's say, we have to use the value for the speed of light in an equation. Normally this would be given as 3x10^8 m/s in the question, but in the tables book it's 2.99792458x10^ 8m/s.

Does that mean we always have to use the full value given in the tables book for every question?

I would, I mean they can hardly take marks off for using what's given too accurately can they?

RP77

Use the exact value for the constants given in the maths tables from now on if they're not given at the end of the question. If a question on Doppler effect for moving stars comes up, rounding off constants could give you an answer outside of the acceptable range. By the way I know it has been mentioned already but I would make sure that I know Boyle's law inside out. Also go over the I versus V graphs for sec A.

Geog ariphic

Okay guys, sorry about that, seems to have been a false alarm. I still won't risk it, but that's reassuring to know.
Pat Doyle the college lecturer? How would he have inside information on this year's marking schemes, unless he was somehow invited to last year's marking conference?

stealinhorses

Yeah, but when the constants were rounded up the last few years, that had a direct effect on the final answer. If we use the ones given in the tables book and our answer at the end is off from the one given in the marking scheme, then we lose marks .

If you used 2.99792458x10^ 8m/s in the c=fλ equation, the answer would have been off by some decimal points and you might have gotten one mark taken off you.

For the particle physics questions over the last few years, they specifically gave the "real" values from the tables book, so that the results would be more accurate (since you're often dealing with the speed of light^2).

So this year, should we use the ones given in the tables and then round up our answer at the end, or leave it, or what do people think? :S

Hollzy

I'm pretty worried about Physics now. It's a weak subject for me and I know I'll be counting it now after the shambles that was honours Maths paper one.... I'm aiming for a B3 but I'm not sure I can get it...

As for predictions... The Boyle's law experiment is a biggy because this year is the 400 year anniversary of his book coming out or something like that.

RP77

I always tell my students to only round off their answers at the very end..do not round off before you plug constants into a formula.

Geog ariphic

stealinhorses wrote: »

So this year, should we use the ones given in the tables and then round up our answer at the end, or leave it, or what do people think? :S

I'm gonna give it to six decimal places accuracy minimum, then round up to two or three (depending on whats standard for the type of question).
That way you have both possible right answers.

I don't seriously see any physics teacher taking marks off someone who is more accurate than the marking scheme.
Just don't round off till the end.

DM360

Geog ariphic wrote: »

Okay guys, sorry about that, seems to have been a false alarm. I still won't risk it, but that's reassuring to know.
Pat Doyle the college lecturer? How would he have inside information on this year's marking schemes, unless he was somehow invited to last year's marking conference?

He's a Leaving Cert Physics teacher in the Institute of Education. According to many he's the best Physics teacher going. In my opinion he's definitely the best I've seen, probably the best teacher overall.

He knows the whole syllabus and exam papers inside-out and would be very high up as far as Physics teachers go. I'd be fairly certain he's well-informed of all goings-on.

Anyway, it's up to the candidate on the day but if you opt for the definition through words and get stuck a bit, you may aswell go for the formula and explaining the symbols. It can do no harm to try both?

nitromaster

Really thinking of dropping down.....anyone got any thoughts on this?

I'm just pretty bad with calculations and shizz....ended up just barely failing the mock...so doesn't boost confidence!

Hollzy

What page are the values for the speed of light and such on in the log tables?

Boyle's Law is a likely experiment because of a 400 year anniversary of his book coming out. Rutherford has a 100 year anniversary for something as well. Joule's Law and wavelength of monochromatic light are also good experiments to go over. And a sound experiment is likely. Maybe a long question on heat then?