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Exam - John C. Kirk — LiveJournal

Jun. 21st, 2002

07:42 pm - Exam

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Well, that's that - my final exam has now been and gone. It wasn't quite what I was expecting, but it basically went ok.

This was more of a general overview than I'd thought - they had questions from the "Waves and our Universe" module, as well as the Fields/Forces stuff, and they relied on general knowledge from the first two modules too (Electricity/Thermal Physics, Mechanics/Radioactivity). Fortunately, I read through all my notes last week, so it was all quite fresh in my mind. Still, I was expecting them to go for the analogies more than they did. Ah well.

I screwed up the timing a bit - at the start of the exam, I estimated a minute and a half per mark. After the first hour (2 hour exam), that was down to 1 minute a mark... I wound up missing out the last part of the last question, but that was only 3 marks or so out of 80, so it shouldn't have too much impact.

A few people left after the first hour, which surprised me. I figured they were either doing really well or really badly, neither of which boded too well for me. From talking to one of the guys afterwards, he'd had to skip about half the questions, so I'm guessing that goes for the others too. Still, it's vaguely reassuring when everyone has trouble with a paper. Also, since we're the first lot through the A2 exams, I suspect they'll be generous with the marks, to "prove" that it's a good idea.

There was one question that was wrong - it said "Why do we measure each electron individually?", when the blurb at the start said "We measure packets of electrons together", so I commented on that in my answer - "Actually, you don't, but the reason you measure the packet is..." I'm not sure whether that will get me credit, or annoy the examiner for acting like a smart-arse.

The main thing I had trouble with was a question about particle acceleration in a Van Der Graaf machine. The idea was that you had a table, with kinetic energy along the top (in electron-volts), and time taken to travel along a section of the tube at the bottom. I was then asked to calculate the velocity for each of the times. My first instinct was to say "kinetic energy = half m v squared", and get it from there. However, since they referred to times, I figured that was a clue that they wanted me to calculate it from that. Scribble, scribble, get rid of those lines... So, in the section they referred to, I had the distance (8.4m) and the range of times. I had a look in the formula section, for uniform acceleration stuff. I figured that that section of tube was after the particle had been accelerated, so u=v, and a=0. After fiddling with a few of the equations, I came up with:

x = ut + 0.5at^2

Therefore:

x = vt

Therefore:

v = x/t

Brilliant! I have now deduced that speed=distance/time. <John slaps self>

Well, once I'd stopped wasting time there, it went a bit more smoothly. I then plotted my results (v squared against KE) on a graph, and was asked whether this backed up the proportional relationship. It didn't - I had a curve, nowhere near a straight line. Hmm. I then spent some more time trying to work out whether "something against something" meant "x against y" or "y against x" (I think the latter), before concluding that it would still be a curve whichever way round I drew it.

So, on the grounds of sticking to the results I have, rather than the ones I'd like, I waffled about mass increasing as you get close to the speed of light (Einstein's equation), which I hope was right. In a situation like this, I'm never quite sure whether this is:

a) Deliberate

b) My mistake

c) Edexcel's mistake (hardly without precedent)

Still, one of the other guys got the same thing out, which is encouraging. One of the others got a straight line, but only because he calculated the velocity from the kinetic energy (using mass of electron constant), so it's not too surprising :) That's one thing that suggests I was right to calculate it the way I did - pretty pointless question otherwise.

Ah well, see what happens in August I guess. With luck, the MSc thing will work out, so I won't need the A in Physics to get into uni.

Afterwards, a few of us went off to the local kebab place to chat for a while. I wasn't sure whether people would want to go out for drinks etc., but it turned out not. Some of them have more exams next week (e.g. Chemistry), others had already made plans. Ah well, never mind. I guess 3:30 in the afternoon may be a little bit early for a drinking binge... We've all sort of arranged to meet up in college in August, when our results come out, so I'll see them all then, if not before. One nice thing when we were chatting about life plans etc. - the others were quite surprised to hear that I'm 27. They would have guessed my age as 23, which is quite flattering :) I like to think that I blend in with my surroundings a bit; if I'm in a student environment in jeans/T-shirt, I look quite young, whereas If I'm in the office, in a suit, I look older. Which bodes well for September - I won't look like I belong in a tweed jacket with elbow patches :)

Now to enjoy all the free time I'll have, without classes/revision/exams! I came back home via Oxford Street, and picked up my weekly comics haul. I also treated myself to a couple of extra things, to celebrate - Britney Spear's new CD ("Britney"), and the DVD of "Bedazzled". Nobody else is back yet - I can see Lorna in the library via the ICSF webcam, so M&M may well be there too. Update - they're not, on their way home now, so hopefully I'll see them soon.

I'm listening to the CD at the moment. It's ok - I mainly bought it for the "I'm Not a Girl, Nor Yet a Woman" track, which I haven't got to yet. Hopefully some of the others will be good too. I saw Bedazzled at the cinema a couple of years ago, and enjoyed it. It was an impulse buy - only 9.99 in Virgin, so I figured "what the heck". I don't think any of the others have seen it, so maybe they'll want to watch it later.

Current Mood: accomplished
Current Music: "Bombastic Love" (Britney Spears)