**Physics...Before/After**

Liveforrugby wrote: »

40 mark window, anyone think they got the A1?

Yup! I was absolutely delighted with the paper. I have never covered Mechanics and didn't study Electricity and I still had choice on the paper!

The Mechanics experiment graph was weird, why did they suddenly tell us to draw the line on the paper itself?

Anyway A1s ALL ROUND !

P.S. The nuclear question was devious the way you had to work out the mass of deutirium and tritium yourself hehe, love it!

iLaura wrote: »

Epsi wrote: »

Theory questions were grand. Maths questions were grand , made a few mistakes overall on maths , but they were fairly minor parts.

Stupid mistake on my part for experiment question 1 , it was badly worded and I thought you were supposed to draw on the graph given to you in the question. Asked the examiner about it afterwards and he said it was okay though and I shouldn't loose any marks for it.

Reckon I got a B1 (Secretly hoping for an A2) overall.

One of the examiners in our school got the principle to ring the SEC, you didn't have to draw the graph or anything, just get the slope. So, basically, you get 15 marks for finding acc due to gravity :P

Overall I'm quite pleased with the paper. Experiments were lovely though I was a bit disappointed that Joules Law didn't come up. Modern physics and particle physics were really nice! The only thing is I wish that capacitors came up. That's on average, 50/56 for me, so it would have helped a bit :P

According to my teacher though, the paper was a bit tricky in places, but overall I found it fine.

But you needed to draw the line of best fit in order to get the slope. You don't get marks for ot. But if you just used a data point as a co-ordinate for the slope, you'll lose marks.

mathstalk wrote: »

I suspect this year's easy paper is an "equal and opposite reaction" to last year's one. Of the 11 mandatory expos I looked over, I was prepared for all 4 on the paper. The question 12 was easy enough, but I think they expect people to be caught out by taking the angle theta as the refracted angle. Anybody any idea what that rainbow question was about in #5? I was tempted to write for the conditions; "Well, the man must have functioning eyesight and he has to be standing outdoors to see the rainbow :P". Oh, and in question 8, was the energy produced 0J? Because the mass appeared to be conserved in the equation. I put down 2 answers there, one with, and one without the neutron produced. What was the force of repulsion between the protons? I used Coulomb's Law, but I had to guess the charge of the protons (I just put 1.6*10^-19) to find the force.

Rainbow:
Rain
Sun
Something else

Q8: you didn't use enough significant figures It was close to 0. You were supposed to use the log tables to find the charge on the proton.

mathstalk wrote: »

I suspect this year's easy paper is an "equal and opposite reaction" to last year's one. Of the 11 mandatory expos I looked over, I was prepared for all 4 on the paper. The question 12 was easy enough, but I think they expect people to be caught out by taking the angle theta as the refracted angle. Anybody any idea what that rainbow question was about in #5? I was tempted to write for the conditions; "Well, the man must have functioning eyesight and he has to be standing outdoors to see the rainbow :P". Oh, and in question 8, was the energy produced 0J? Because the mass appeared to be conserved in the equation. I put down 2 answers there, one with, and one without the neutron produced. What was the force of repulsion between the protons? I used Coulomb's Law, but I had to guess the charge of the protons (I just put 1.6*10^-19) to find the force.

I got a mass defect, for q8?

Cathalog wrote: »

But you needed to draw the line of best fit in order to get the slope. You don't get marks for ot. But if you just used a data point as a co-ordinate for the slope, you'll lose marks.

Well, luckily for me, I read the question wrong and just re-drew out the graph, drew line of best fit and then got the slope. I know one of the lads in my centre ended up putting the exam paper into the answer booklet :P

finality wrote: »

How did you do that?

Deuterium has one proton and one neutron.
Tritium has one proton and two neutrons.

Masses of both the proton and the neutron are in the log tables.

BAZINGA!

subz3r0 wrote: »

Deuterium has one proton and one neutron.
Tritium has one proton and two neutrons.

Masses of both the proton and the neutron are in the log tables.

BAZINGA!

that kind of ignores the fact that part of the mass is the actual bonds, not just the sum of the individual parts, ie if you just used that, you'd get the right hand equal to the left hand side?

ehshup wrote: »

that kind of ignores the fact that part of the mass is the actual bonds, not just the sum of the individual parts, ie if you just used that, you'd get the right hand equal to the left hand side?

What?

No, I got a decent mass-defect and the final answer seemed to be in the right magnitude for these kind of questions.

iLaura wrote: »

Cathalog wrote: »

Back of logtables give you the mass of H-3 and H-2 in terms of u.

Once you made sure to convert them to Kg :P a.m.u = bane of my existance. I spent forever trying to find the mass of an electron -.-

Yeah, amu sorta pissed me off. Mass of electron is given in Joules on page 46 btw :P
And you use page 47 2nd last line to convert from amu and kg.

mathstalk wrote: »

What was the force of repulsion between the protons? I used Coulomb's Law, but I had to guess the charge of the protons (I just put 1.6*10^-19) to find the force.

I used Newton's law of universal gravitation.. Only thing I could think of doing without having the protons charges.

Overall pretty annoyed with the lack of given values in questions. Yes it wasn't too bad and yes I did get the values myself, but I had to waste time flicking through the log tables to find many of those values for the calculations. Felt more like a test of who could find the information they need the fastest at times.

yeah, there was a lot of turning pages in the log tables trying to find the values of the constants. i mistakenly used 3x10^8 m/s for c, as opposed to 2.99792x10^8, they'd hardly take off more than a mark for that?

iLaura wrote: »

One of the examiners in our school got the principle to ring the SEC, you didn't have to draw the graph or anything, just get the slope. So, basically, you get 15 marks for finding acc due to gravity :P

Oh thank God! I'm just reading over the question now and it makes no sense if you think about it, "Draw the appropriate graph on this examination paper." Just think about it, what does that actually mean? Draw a graph on the pink question paper you were given? Why would you do that and how would they know you did it if you take the examination paper home with you? Anyway, I drew the line, found the slope and did g=4pi^2(slope)^-1. Really though, first question and they made an error? But wait, there's more. Look at question 6. I quote: "four minutes and 36 seconds more were needed to take him down to 5km". Er, 5km from what exactly? from the ground or from the plane? And again, question 12 b). Quote: "What would be the value of theta so that the ray of light emerges parallel to the side of the glass block?" What side? The glass block has four sides. Theta would be 48 degrees if they mean the top or bottom sides and it would be 90 degrees if they mean the right or left sides.

Seriously, I've had the paper for about 4h now and I've already noticed so many errors, most of which I noticed on first glance. Aren't the papers supposed to be checked multiple times before they're given out?

finality wrote: »

Nah. I just multiplied the mass number by u, I was trying to find their masses in terms of u but didn't know where to look... it's pretty unfair that I knew what to do but just not where to look.

I did 5, 7, 8, 9, 10(a), 12(a)(b) I think.

that's what I mean. People didn't have practice finding those values using the log tables. I was just lucky that I stumbled across it before.

MatthewRud wrote: »

I used Newton's law of universal gravitation.. Only thing I could think of doing without having the protons charges.

Overall pretty annoyed with the lack of given values in questions. Yes it wasn't too bad and yes I did get the values myself, but I had to waste time flicking through the log tables to find many of those values for the calculations. Felt more like a test of who could find the information they need the fastest at times.

But didn't it say repulsive force? Gravitational force is always attractive.

mathstalk wrote: »

Quote: "What would be the value of theta so that the ray of light emerges parallel to the side of the glass block?" What side? The glass block has four sides. Theta would be 48 degrees if they mean the top or bottom sides and it would be 90 degrees if they mean the right or left sides.

You draw the normal line on the thing to help you. In either case, the symbol theta was drawn on the angle they want you to find.

I did q1-3, 5, 7, 8, 10a, 11 and then did 12b, c and d, even though our teacher warned us against doing an extra question.

For the repulsive forces, I did Coulumbs Law too, because in the question it said something about free space and that was the only formula that I could see that had epsilon in it.

I'm just so glad that my teacher did particle and modern physics revision with us, otherwise that paper would have been torture.