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# Official Thread For OCR Physics A G484 Jan 2011 Watch

1. (Original post by jamesgil007)
Hey!

Had some spare time at the end of the exam so scribbled down my answers to most Q's
(Not sure they are all right but most I think(Hope!))

1ai) Sum of the momentum before the collision equal to the sum after, if no external forces are applied
ii) Energy no conserved
iii) v=1.333 ms^-1
iv) KE before bigger than after ( Ke1= 13 Ke2= 3.something)
bi) 6123Kg
ii) 72000Kgms^-1
14400N
1500Kg

2i) Resultant force towards centre
ii) V changing directed towards centre
ci) Thursters in direction of velocity (there are more answers)
ii) 4500ms^-1

3i) Unit where 1000 watts is transformed in an hour (Dunno how to word it?)
Cost=£1.41
Energy removed 114000
Rate= 19

Graph of milk- negative line from 18 then past 0 steeper negative line (Not sure if you have to include straight line along 0)

A=2.5m
T=2.22x10^-5
Vmax=3.5x10^-4 ms-1
x= 2.5cos(2(pi)2.2x10^-5t) (not sure if sin or cos?)

450 ms^-1

y=1/x, y=x

n= 8.4
mass= 0.023

Yeah sorry left out some of the wordy questions!
1aii) kinetic energy not conserved
2. i got 8.4 moles for the penultimate question but i got something like 8.3 or 8.2 in moles for the next question which i then converted to grams, did anyone get this?
3. I had OCR chemistry yesterday undoubtedly the worst paper I have ever done. Then the following day, is the Physics paper which was almost as bad as the specimen paper. I hope edexcel don't screw up M2 tomorrow or I'm dead.
4. (Original post by rainbowsss)
1aii) kinetic energy not conserved
I hope I get the marks for showing it was perfectly inelastic. I showed the speed of separation is 0 and hence e is 0. It's correct physics but not in our course.
5. eurghh :/ for the force question did anyone else not read it properly and just go for mv^2/r ?
6. (Original post by ViralRiver)
I got the milk gradient thing fine, took a while to think of which one had the steeper gradient. How did people to the boyle's law graphs? I had like a y=1/x graph for the one on the left, then a y = x one for the one on the right?

How did you work out the mass of the helicopter oO?
If the helicopter is hovering the lift force = the weight

the force was something like 144000N so this = mg

Mass = 144000/g = 1.5x10^3 Kg
7. (Original post by k9markiii)
I hope I get the marks for showing it was perfectly inelastic. I showed the speed of separation is 0 and hence e is 0. It's correct physics but not in our course.
Nice bit of M2 practice for tomorrow! You should get the marks, but having said that OCR are notorious for only accepting keywords, so might only accept one method.
8. (Original post by jamesgil007)
x= 2.5cos(2(pi)2.2x10^-5t) (not sure if sin or cos?)
I think it is

d= 2.5cos(2(pi)2.2x10^-5t) +15.5

9. ahh hell!!
i cant even remember a milk question and having to draw graphs of milk!!
really hoping thats not coz i didnt see the question!!

can anyone remember what this question was?
10. Thought it was cheeky of OCR to put that KwH question in, I defo go it wrong, I did pretty bad in this paper.
11. Yeah, I'm pretty sure I've got all this exam wrong. Most difficult physics exam I've ever sat. The June one of G484 was so much easier, this one was just taking the mick.
12. (Original post by k9markiii)
I had OCR chemistry yesterday undoubtedly the worst paper I have ever done. Then the following day, is the Physics paper which was almost as bad as the specimen paper. I hope edexcel don't screw up M2 tomorrow or I'm dead.
Oh godd... I know what you mean. The C3 a few days ago was very hard (relative to other past papers). Pleaseeeee let this M2 be easy.
13. (Original post by jamesgil007)
Hey!

Had some spare time at the end of the exam so scribbled down my answers to most Q's
(Not sure they are all right but most I think(Hope!))

1ai) Sum of the momentum before the collision equal to the sum after, if no external forces are applied
ii) Energy no conserved
iii) v=1.333 ms^-1
iv) KE before bigger than after ( Ke1= 13 Ke2= 3.something)
bi) 6123Kg
ii) 72000Kgms^-1
14400N
1500Kg

2i) Resultant force towards centre
ii) V changing directed towards centre
ci) Thursters in direction of velocity (there are more answers)
ii) 4500ms^-1

3i) Unit where 1000 watts is transformed in an hour (Dunno how to word it?)
Cost=£1.41
Energy removed 114000
Rate= 19

Graph of milk- negative line from 18 then past 0 steeper negative line (Not sure if you have to include straight line along 0)

A=2.5m
T=2.22x10^-5
Vmax=3.5x10^-4 ms-1
x= 2.5cos(2(pi)2.2x10^-5t) (not sure if sin or cos?)

450 ms^-1

y=1/x, y=x

n= 8.4
mass= 0.023

Yeah sorry left out some of the wordy questions!

Holy Sh1t!!!
I wrote 5 by accident.
Do you think i'll get ECF?
I can't believe I did that.
14. What was the thing you could do to shift the orbital position temporarily?

Question 2 I think.
15. (Original post by pianofluteftw)
Well, for starters while kWh is not on the syllabus, it does STATE that all previous knowledge is assumed (Gave me a nice easy few marks!)

The helicopter I also really enjoyed! I wasted too much time proving it in two ways though :/ ah well

The amplitude was indeed 2.5, and I put the displacement being x=2.5cos(2pif)t + 13 (I think f was 1.22x10^-5) and wrote a note to the examiner saying it must be from the maximum or minimum.

And the tide does illustrate simple harmonic motion! Not only springs do (I mean a woodwind instrument is a prime example). As long as acceleration is directly proportional to displacement, and is always directed towards the mean it shows simple harmonic motion. Not just springs.

And the satelite one was easy, just equate gravitational force to centripetal force and rearrange having cancelled the small 'm's and the radius.

Plus the laws have names for a reason - they were credited to the scientist that came up with them. And they are not hard to state in words or learn! Like we call the Boltzmann constant just that, or Newton's three laws.

Bit of a weird paper but none of it hard... or is it just me that thought that? Plus we'd done both Jan and June '10 past papers and specimen and it wasn't really any harder and all was on the syllabus?
I've yet to read the other posts, but did it not ask for an equation for depth, not displacement? Also how on earth does that equation produce a depth of 18m, surely you've got the wrong equilibrium point there, or did I misread the question?
16. Can someone confirm d=15.5 + 2.5sin(2pift)?
Obviously I replaced the f, but did the question not say the water was initially calm ie at 15.5m, thus cos would be wrong as the tide would go from 15.5 to 18 to 13 etc... I suppose 15.5 -2.5sin(2pift) would also be OK as it didn't state whether or not the tide goes up or down firstly. Hmm...

For the 3 mark graph question, I appreciate that E-mctheta means the gradient under the x axis is larger, but as it was negative I couldn't decide whether it was less negative etc.
17. i got the amplitude wrong, will i get ECF for the maximum velocity question which u needed to use Vmax=2pifA??
18. (Original post by CoffeeStinks)
What was the thing you could do to shift the orbital position temporarily?

Question 2 I think.
I said dock something onto it to increase the mass hahaha! I left it till the last minute so scribbled something down before the paper was taken from me
19. hi there. please did anyyyyyyone get questions 2 for the orbit of the satelite around the earth. i didnt get any of the marks for that question. pelase someone help, my brain is fried
20. (Original post by rob...)
I said dock something onto it to increase the mass hahaha! I left it till the last minute so scribbled something down before the paper was taken from me
I was thinking that too but then I thought that it said briefly change orbit, so I wasn't sure if that could be classed as temporary.

How did you find the paper on the whole?

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