OCR Physics A G484 - The Newtonian World - 11th June 2015 Watch

Elcor
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#541
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#541
(Original post by shorty.loves.angels)
Might be wrong (I should know!) but I think it means that the student may just give the rounded A0 answer and it should be awarded. Although, if I looked at the Q I would probably have a better idea.

If I was going to advise you, I would round your value appropriately to show the answer for the 'proof' just in case, though it will most likely be awarded.
Do you mark for OCR?
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xy0mz
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Why is g (acceleration of free-fall) maximum at poles & zero at the equator??


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xy0mz
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(Original post by xy0mz)
Why is g (acceleration of free-fall) maximum at poles & zero at the equator??


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EDIT ***I meant why is it zero at poles and maximum at equator****


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shorty.loves.angels
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(Original post by Elcor)
Do you mark for OCR?
No I mark students' papers, but I'm pretty sure I've had this discussion with OCR minions :pinch:

Note: My advice is purely my own based on differences I've seen that do require/ don't require justification of the proof.
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gothmog827
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#545
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are you supposed to draw the field lines within a shape as well as outside? Thanks
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Chung224
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#546
oh my god i have no resources to revise, done the past papers answered questions in text book/ redo notes what now
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shorty.loves.angels
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(Original post by gothmog827)
are you supposed to draw the field lines within a shape as well as outside? Thanks
Not usually.

For gravitational fields of a spherical object mark schemes usually say that lines are directed towards the centre, as judged by the eye - in other words, they won't meet at the middle but should if they were extended.

Hope this helps.
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Chung224
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#548
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(Original post by BrokenS0ulz)
Just thought I'd let you guys know that if you've run out of questions there's some more available by edexcel. Just type in physics a level edexcel. The formats slightly different but I think they're still useful.
thy questions are all jumbled up so i have to pick out the type of questions i want to write, but good suggestion though
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Elcor
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(Original post by xy0mz)
Why is g (acceleration of free-fall) maximum at poles & zero at the equator??


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(Original post by xy0mz)
EDIT ***I meant why is it zero at poles and maximum at equator****


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If that were true we would have an epidemic of people falling off of the North Pole and Antartica and floating out into space.
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Chung224
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(Original post by Elcor)
If that were true we would have an epidemic of people falling off of the North Pole and Antartica and floating out into space.
That made me laugh.
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L'Evil Fish
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#551
(Original post by Elcor)
If that were true we would have an epidemic of people falling off of the North Pole and Antartica and floating out into space.
Would be a good way to reduce the population
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Elcor
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#552
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(Original post by Chung224)
That made me laugh.

Glad to be of service

(Original post by xy0mz)
EDIT ***I meant why is it zero at poles and maximum at equator****


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I'm guessing you mean "why is the reaction force from the floor maximum at the poles and minimum at the equator?" So, to answer the question properly:

At the equator you're traveling in a circle of radius equal to the Earth's radius. Resolving forces gives mg-R=mv^2/r, so R=mg-mv^2/r
At the poles, you're just spinning; you have no actual displacement due to the Earth rotating and so you're not traveling in a circle at all. Resolving forces gives R=mg
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BrokenS0ulz
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#553
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(Original post by Elcor)
If that were true we would have an epidemic of people falling off of the North Pole and Antartica and floating out into space.
Oh god hahaha

(Original post by Chung224)
That made me laugh.
I found some more question, AQA has got some on their alevel physics page, their unit 4 has got some g484 type stuff.
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Chung224
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(Original post by BrokenS0ulz)
Oh god hahaha



I found some more question, AQA has got some on their alevel physics page, their unit 4 has got some g484 type stuff.
oohh ok cheers :P
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BrokenS0ulz
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#555
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(Original post by Elcor)
Glad to be of service



I'm guessing you mean "why is the reaction force from the floor maximum at the poles and minimum at the equator?" So, to answer the question properly:

At the equator you're traveling in a circle of radius equal to the Earth's radius. Resolving forces gives mg-R=mv^2/r, so R=mg-mv^2/r
At the poles, you're just spinning; you have no actual displacement due to the Earth rotating and so you're not traveling in a circle at all. Resolving forces gives R=mg
Why isn't R at the equator mg+mv^2/r? I thought you would add the weight and the centripetal force to get the contact force
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Elcor
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(Original post by BrokenS0ulz)
Why isn't R at the equator mg+mv^2/r? I thought you would add the weight and the centripetal force to get the contact force
Don't think about the centripetal force as its own thing - it's simply caused by the weight-reaction pair. You know the centripetal force acts towards the centre of the Earth like your weight, so if you resolve downwards you get my equation.
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Shabz12357876877
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#557
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#557
does anyone know where i can get the answers for the questions in the physics 2 ocr advnaced science by cambridge coas book? i lost the cd and i cant find it online i just ened the g484 ones please
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MysteriousKnight
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Hi Peeps!

I have one request ... can someone please draw the diagram for measuring the specific heat capacity of a liquid and a solid please!

Hows everyone generally feeling about the paper anyway?

Thanks in advance!
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sagar448
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(Original post by Elcor)
Don't think about the centripetal force as its own thing - it's simply caused by the weight-reaction pair. You know the centripetal force acts towards the centre of the Earth like your weight, so if you resolve downwards you get my equation.
He's right you know. Gravity is weaker at the equator because when the earth is rotating, at the equator the there is a bulge (caused by centrifugal force) and since the bulge increases the distance from the centre (not a very big increase) gravity at the equator is less than at poles.
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Oraeng
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This exam genuinely terrifies me.. just got the feeling that it's going to be a repeat of G481 last year and I'll flunk out and get a C or worse. I NEED and A
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