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OCR Physics A Breadth of Physics (24th May 2016) Discussion

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Original post by mahmzo
So to finalise. The exam wont be any more difficult then the previous spec? Obviously there will be tough questions to target those achieving an A but other than that should it be the same?


That's a separate point to the one I was making, but yes. The new spec is supposed to be the same level of difficulty as the old spec. Someone who could get an A in the old spec should get an A in the new spec. However, you should remember that there is content (practical skills and a couple of topics) in the new spec exams that was not in the old spec exams.
Original post by violavenisis
Rounding your answers is definitely important- as a standard rule you should round to the lowest number of sig. figs given in the question. For example, if you were trying to calculate velocity and were given t=1.45s and s=23m, then you'd give your answer to 2 significant figures (as displacement is quoted to two s.f.)


Not quite the case. In most questions, two or three significant figures is acceptable. In fact, OCR won't ever penalise you for using more than 3sf and will (in theory) only penalise you once per paper for using 1sf.

However, the exception to this is those specific questions that ask for an appropriate number of sig fig. Then your rule described above applies. This would be maybe one question per paper.
Original post by Abeh
https://drive.google.com/file/d/0Byy0joJp_zfMSUJmTjVpcFpYME0/view?pref=2&pli=1

Someone posted this on a physics YouTube video, its a document with over 1000 multiple choice questions on! Not all of them will be relevant but they seem quite useful, it could be good practice to have a go at a few before Tuesday :smile:


youre welcome lol
Reply 123
Avatar for voltz
voltz
6
I've got a few questions, if someone could help me out:

Would I be correct in saying the voltage is the same across each branch in parallel, and the voltage is shared dependant on the resistance?

I seem to get confused about how voltage is shared on a branch - could some please clarify this?
Original post by cowenphysics
Not quite the case. In most questions, two or three significant figures is acceptable. In fact, OCR won't ever penalise you for using more than 3sf and will (in theory) only penalise you once per paper for using 1sf.

However, the exception to this is those specific questions that ask for an appropriate number of sig fig. Then your rule described above applies. This would be maybe one question per paper.


True- but at times quoting the incorrect sig figs would show a lack of understanding. For example, if you were calculating the uncertainty of a value, you wouldn't quote it to more significant figures than the best value (in the form best value= mean±uncertainty). Surely if you did, this would be marked as incorrect?
Can anyone explain to me questions about pressure under water.... I just don't understand 😭


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Original post by Chlo.Harr
Can anyone explain to me questions about pressure under water.... I just don't understand 😭


Posted from TSR Mobile


Guessing your talking about Archimedes Principle, and p = hpg.

With Archimedes Principle you need to remember his law, that upthrust is = weight of fluid displaced.

p = pressure
h = height from object to air
p(rho) = density
g = gravitational field strength.

They would usually give you the values I think, looking at past papers lol.
How ever if you are asked to prove it

we know P = F/A

F = Weight
Weight = mg

m = p(rho) x Volume (Area x Length(h))

substitute back, Weight = pAhg

therefore: P = pAhg/A

A's cancel.
Yeah I can prove it 👍🏻 I get the physics but I can't do the questions on it 😔 thanks for the overview though!!


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Aghhh the exam is tomorrow!!

Does anyone know any useful websites that go through all of the practicals we have done, plus questions on experimental uncertainty?

The mock was so heavily weighted on the uncertainty stuff, I know it (hopefully) won't be the same in the exam tomorrow, but I kinda need to work on that!!

Thanks :smile:
Original post by cweyland
Aghhh the exam is tomorrow!!

Does anyone know any useful websites that go through all of the practicals we have done, plus questions on experimental uncertainty?

The mock was so heavily weighted on the uncertainty stuff, I know it (hopefully) won't be the same in the exam tomorrow, but I kinda need to work on that!!

Thanks :smile:


Give this a watch

https://www.youtube.com/watch?v=JCdukQADyc8&list=WL&index=504
Will we need to know the experiments for the Breadth or Depth Paper?
Original post by mm_7
Will we need to know the experiments for the Breadth or Depth Paper?



The actual experiments is for the depth. However you will need to apply your experimental knowledge to both papers. Look at the specimens so you know how it will be
Original post by mahmzo
The actual experiments is for the depth. However you will need to apply your experimental knowledge to both papers. Look at the specimens so you know how it will be


What do you mean exactly by apply experimental knowledge? What sort of experiment Qs could they ask in the Breadth?
Which topics tend to have the hardest questions? Are there any topics which are likely to come up in tomorrows paper?
I was told by my teacher that most of the practical questions are gonna be on the depth paper so i've barely read over them, do we reckon theres gonna be lots on the practical stuff for the breadth tomorrow?
Original post by mahmzo
Guessing your talking about Archimedes Principle, and p = hpg.

With Archimedes Principle you need to remember his law, that upthrust is = weight of fluid displaced.

p = pressure
h = height from object to air
p(rho) = density
g = gravitational field strength.

They would usually give you the values I think, looking at past papers lol.
How ever if you are asked to prove it

we know P = F/A

F = Weight
Weight = mg

m = p(rho) x Volume (Area x Length(h))

substitute back, Weight = pAhg

therefore: P = pAhg/A

A's cancel.


I really don't understand that ^ :frown: I know how to answer questions on it. but don't know how to prove it. Help lol.
Original post by mahmzo
Guessing your talking about Archimedes Principle, and p = hpg.

With Archimedes Principle you need to remember his law, that upthrust is = weight of fluid displaced.

p = pressure
h = height from object to air
p(rho) = density
g = gravitational field strength.

They would usually give you the values I think, looking at past papers lol.
How ever if you are asked to prove it

we know P = F/A

F = Weight
Weight = mg

m = p(rho) x Volume (Area x Length(h))

substitute back, Weight = pAhg

therefore: P = pAhg/A

A's cancel.


Finally got it. I Think. Hopefully.
Original post by mahmzo
PM me your number. I am creating a new groupchat


another guy already made one
Any predictions of grade boundaries out of 70 for an A?
https://d257ba8b9971d35b509279e471f1d8167ae3e7f0.googledrive.com/host/0B1ZiqBksUHNYZkdjdXdsZmZjX3M/From-Edexcel-Set-A/2.5%20Quantum%20Physics.pdf

Last part of question 1 anybody?

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