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ocr b - lets have some answers watch

1. How did you all find it today? I thought it was pretty good, not too bad - except the one where you have to explain 3 superposition affects or something along those lines. I did standing waves, but found it hard to try to find three. What about why the waves creat a maximum every 30 seconds. I used the sin(2*pi*f*t) thing, both are equal with the different frequencies at 30 seconds. I thought the lorry question was easy, but only because i do mechanics, it would be really hard if you didnt! Most of the second paper is easy marks for mechanics people, which is unfair for the rest of the candidates. What did you put for how to retardation force on the changes, i settled with "the wheels may sink into the gravel increasing the force" mainly because i couldnt think of any other ones!

any other difficult questions?
2. Yeah THREE superpostion effects was annoying, i just waffled on, hoping it would cover enough. The lorry question was alrite apart from the last part of it, i couldnt do that. The 30 second question about phasors, i just put how 6 and 5 are factors of 30, so they line up every 30 seconds...lol ive never even heard of the 'sin(2*pi*f*t) thing'
3. the lorry bit you could work out by
grav.pot. energy = k.e + W.D

W.D = F x d
4. (Original post by neb_revlis)
The 30 second question about phasors, i just put how 6 and 5 are factors of 30, so they line up every 30 seconds...lol ive never even heard of the 'sin(2*pi*f*t) thing'
OMG, where was that question, i don't remember seeing it?
5. lol, you do remember it, it was the one about surfers trying to catch waves, i just dont think anyone did it the way i did
6. (Original post by riddles55)
lol, you do remember it, it was the one about surfers trying to catch waves, i just dont think anyone did it the way i did
oh yeah that one. it was the one i didn't seem to get. I could work out the amplitude thingy and all that. just couldn't draw the phasors right. I got pretty confused
7. The examiners are really running out of ideas, and equation to find out how long an egg takes to cook, ..at least it was easy marks i suppose
8. (Original post by neb_revlis)
The examiners are really running out of ideas, and equation to find out how long an egg takes to cook, ..at least it was easy marks i suppose
did you get k to be almost the same for each egg? like 7000 and something
9. Yeah, but not quite the same. Does anyone know what the grade boundaries normally are for these papers (also does anyone happen to know how many marks are normally needed for 100 UMS)?
10. (Original post by ljfrugn)
Yeah, but not quite the same. Does anyone know what the grade boundaries normally are for these papers (also does anyone happen to know how many marks are normally needed for 100 UMS)?
for an A its 88/110 for Understanding processes and;
80/100 for Physics in Action

I don't have the info about the lower boundaries to hand, but i think they're in one of the academic forums on here
11. The 88 is just a standardised mark though, isn't it? Not the actual raw mark that you normally need to get. I was asking about the 100 (or 110 it seems) UMS boundary because it would really help me to get full UMS on this exam - I didnt do too well on my courseworks and would like things a bit easier next year.
12. (Original post by ljfrugn)
The 88 is just a standardised mark though, isn't it? Not the actual raw mark that you normally need to get. I was asking about the 100 (or 110 it seems) UMS boundary because it would really help me to get full UMS on this exam - I didnt do too well on my courseworks and would like things a bit easier next year.
no that is the UMS boundaries, not the raw marks
13. so few people do ocr b! I think uni's think ocr b is a doss, and everyone says they are right... I thought it was easy, so i guessed i was good at physics... guess not.

Right, back to A2 revision, GM/r^2, GM/r^2, GM/r^2
14. btw, in case you didnt realise, my previous post was a bump
15. (Original post by riddles55)
I think uni's think ocr b is a doss, and everyone says they are right...
I hope you're wrong, what gives you this idea? My teachers say that OCR is the hardest exam board for sciences.

Personally though, I did the exams yesterday and found them quite easy. Even so, it's still quite hard to judge what UMS i'll get.
16. I found it ok apart from the lorry question. What did everyone get for that final part? I ended up with 39m or something.

For the egg question, my conclusion was that the answers were nearly equal but there was a margin of error. This could have been because the source data was rounded.
17. I concluded the same thing as you for the egg question.

I didn't get the lorry question, but 39m is the answer that a few people had after the exam finished. Seems like you got it right
18. the egg question jsut said "state", was only 1 mark, and so you only had to say that the relationship was true, without giving any reasons or justifying your answer (assuming it was true, which is what i put)
19. Sounds good to me

Does anyone know what raw mark was needed for 80% UMS over the past few years?
20. I did Young's Slits for section C. May 3 things you could see were alternating bright and dark bands because of superposition, bands get less vivid further from centre because one wave has travelled further so loses amplitude and angle to first maximum is proportional to wavelength because w=dsinT, so T=sin^-1(w/d).

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