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OCR Physics A G485 - Frontiers of Physics - June 2016

I won't be revising for a while but if I can help, I'll try, means less revision for me in the summer if I help people earlier on (or if people explain to me!)

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June 2011 Question 7cii

Suggest a reason wiy it is difficult to predict the future of the universe.

I put uncertainity of the hubble constant.

That is fine.

But the answers say, that it could be:

existence of black holes/dark matter/dark energy etc.

My question is why are these existences such that it makes it difficult?

Thanks x
http://www.ocr.org.uk/Images/81115-unit-g485-fields-particles-and-frontiers-of-physics-specimen.pdf

For 1di why does the discharge in the voltmeter cause the capacitor to discharge slowly?
Is question 3 for the electron scattering experiment in our spec
Original post by Mihael_Keehl
June 2011 Question 7cii

Suggest a reason wiy it is difficult to predict the future of the universe.

I put uncertainity of the hubble constant.

That is fine.

But the answers say, that it could be:

existence of black holes/dark matter/dark energy etc.

My question is why are these existences such that it makes it difficult?

Thanks x


I think it's because the future of the universe is determined by the density of the universe- whether it is an open, flat or closed universe.
We do not know the density of the universe due to the existence of black holes, dark matter and dark energy because we do not know their density.

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Original post by flowerspace
I think it's because the future of the universe is determined by the density of the universe- whether it is an open, flat or closed universe.
We do not know the density of the universe due to the existence of black holes, dark matter and dark energy because we do not know their density.

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Thank you that makes sense.
Original post by Mihael_Keehl
Thank you that makes sense.


Yeah because you know like the critical density, if the density of the universe is > the critical density, then it's a closed universe
Density < critical density then it's an open universe
Density = critical then it's a flat universe

Glad I helped :smile:

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Original post by Mihael_Keehl
Is question 3 for the electron scattering experiment in our spec


Yeah I think it's the Rutherford one, where they had alpha particles and the gold foil

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Original post by flowerspace
Yeah I think it's the Rutherford one, where they had alpha particles and the gold foil

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Thank you the first part is, the latter part I found you can use the blockers of say paper which will block out paper etc.
Original post by flowerspace
Yeah because you know like the critical density, if the density of the universe is > the critical density, then it's a closed universe
Density < critical density then it's an open universe
Density = critical then it's a flat universe

Glad I helped :smile:

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I thought that the universe was flat as that supports the Big Bang Theory.

Yes I follow what you mean.

Closed Universe = The universe will eventually contract and cause the big crunch

Open Universe = The universe will expand forever.

Flat Universe = The universe will expand towards a finite limit.
Original post by Mihael_Keehl
I thought that the universe was flat as that supports the Big Bang Theory.

Yes I follow what you mean.

Closed Universe = The universe will eventually contract and cause the big crunch

Open Universe = The universe will expand forever.

Flat Universe = The universe will expand towards a finite limit.


Yes I think that as far as we know the universe is flat- the density is very close to the critical density. But I don't know if it supports the big bang theory or not

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Original post by flowerspace
Yes I think that as far as we know the universe is flat- the density is very close to the critical density. But I don't know if it supports the big bang theory or not

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I suppose yes that is a true assesment.

Are you giving this exam in june :smile:
Original post by Mihael_Keehl
I suppose yes that is a true assesment.

Are you giving this exam in june :smile:


Yeah I want to do physics with Astrophysics at uni :smile: :smile:

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Original post by flowerspace
Yeah I want to do physics with Astrophysics at uni :smile: :smile:

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Ah nice, how is revision going?

Have you looked at last years papers yet?
Original post by Mihael_Keehl
Ah nice, how is revision going?

Have you looked at last years papers yet?


Revision is well, haven't looked at last year's yet as we're having it as a mock.
You?

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Original post by flowerspace
Revision is well, haven't looked at last year's yet as we're having it as a mock.
You?

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Yes decent. Module 1 should be fine, M2 needs more work.

First question is trickyish somewhat of g484 june 2015.. gl
Original post by Mihael_Keehl
Yes decent. Module 1 should be fine, M2 needs more work.

First question is trickyish somewhat of g484 june 2015.. gl


Ok :smile:

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What is the diffreence between average density and critical density?
The average density is the average density of the universe, since this value varies depending on where you are in in the universe and the critical density is the density required for the universe to have a strong enough gravitation pull to stop its expansion.
For the defintiontio of Magnetic Flux:

Magnetic Flux = Magnetic Flux Density * Area at normal to the field/flux

Is it field or flux or both? :smile:

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