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OCR Physics A G485 - Frontiers of Physics - 18th June 2015

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please can someone link me to the unofficial mark scheme
What did people write for the 1 marker on the overhead cables floating?


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Original post by Alex103
First parts of paper were harder than later parts I thought! Was really hoping for 7 mark MRI scan question but no :frown:
Hope I did enough, made some mistakes, couldn't get answer for horizontal displacement one. Oh well enjoy summer and wait for August


Yeah, the 2nd half of the paper was nice in comparison to the electricity stuff.
What do you think the boundaries will be?
I'm kind of worried now:rolleyes:

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Original post by matthew6665
Well I don't know which unis give such high offers.. 2 people I know are going Oxbridge and both have AAA offers :s So I guessed that ****ter unis will not have A* offers cause that's just mad.


...I have an A*AA offer to Bristol so thats clearly not the case
Original post by kieran2405
What did people write for the 1 marker on the overhead cables floating?


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Magnetic field too weak to present a magnetic force to equal the weight force

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Original post by Leechayy
Magnetic field too weak to present a magnetic force to equal the weight force

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I went for "current is alternating so magnetic force produced would continuously fluctuate upwards and downwards".
Original post by kateyl
Yeah I did all that but for some reason I got 60% i think not 64... not sure what happened in my calculation 8(


Did it ask for percentage or fraction?I wrote 0.64 as in the fraction...ffs
Original post by Deniderveni
I said the same thing but no, that's wrong. It does accelerate through the pd, then it accelerates towards the same direction (because it came from the positive side of the field) BUT, and I'm kicking myself for forgetting the basics of physics, LEFT. HAND. RULE! The field is exerting another perpendicular force on it, so it should be parabolic!

Although this is what my friends told me. It makes perfect sense, but I'm not sure which vertical direction it would curve in :/


Oh thank God:p:p:tongue:

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Original post by Deniderveni
I said the same thing but no, that's wrong. It does accelerate through the pd, then it accelerates towards the same direction (because it came from the positive side of the field) BUT, and I'm kicking myself for forgetting the basics of physics, LEFT. HAND. RULE! The field is exerting another perpendicular force on it, so it should be parabolic!

Although this is what my friends told me. It makes perfect sense, but I'm not sure which vertical direction it would curve in :/


Don't understand this at all. Doesn't the LHR only apply to magnetic fields?
I said it goes through hole
Slows down due to repulsion
Eventually attracted back to plate A

It said no weight component so no vertical displacement

And it was an electric field so no left hand rule or anything
Original post by L'Evil Fish
I said it goes through hole
Slows down due to repulsion
Eventually attracted back to plate A

It said no weight component so no vertical displacement

And it was an electric field so no left hand rule or anything


I said the field would take out 6eV of KE so it must reverse (since it had 4eV)
Original post by L'Evil Fish
I said it goes through hole
Slows down due to repulsion
Eventually attracted back to plate A

It said no weight component so no vertical displacement

And it was an electric field so no left hand rule or anything



People are making me panic here haha, I am 1000000% sure there was no magnetic field involved in it!
Original post by L'Evil Fish
I said it goes through hole
Slows down due to repulsion
Eventually attracted back to plate A

It said no weight component so no vertical displacement

And it was an electric field so no left hand rule or anything


ohhhhhh i thought the it was negative plate at A and positive at B.
Well.. its been fun guys
Original post by Raizel
ohhhhhh i thought the it was negative plate at A and positive at B.
Well.. its been fun guys


Same, rest in pieces:colonhash:

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Original post by kieran2405
What did people write for the 1 marker on the overhead cables floating?


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I said the force due to the field would oscillate so the cable would oscillate :s

Original post by Leechayy


No you don't, 0.01 goes into X-rays so 0.99 goes into heating the anode. For the next part you use the whole kinetic energy of 1 electron though, because that would produce the most energetic X-ray possible.
Original post by L'Evil Fish
Those are humanities at Oxford.

Cambridge offers are A*A*A for sciences

And somehow I don't think Cambridge is ****ter

Manchester Physics A*A*A

Cambridge, Imperial, Warwick, Manchester all give higher offers


Need the A*s for Manchester Physics, think they'll probably let me in with one A* though.
Original post by L'Evil Fish
I said it goes through hole
Slows down due to repulsion
Eventually attracted back to plate A

It said no weight component so no vertical displacement

And it was an electric field so no left hand rule or anything


This is exactly what I put! Why are people confusing things :frown:
Is the unofficial mark scheme out?
Original post by Elcor
I said the field would take out 6eV of KE so it must reverse (since it had 4eV)

I didn't qualify my answer, probably should have
Original post by actanide
People are making me panic here haha, I am 1000000% sure there was no magnetic field involved in it!

Yeah there wasn't
Original post by Raizel
ohhhhhh i thought the it was negative plate at A and positive at B.
Well.. its been fun guys

It didn't say which was charged, it just had the field lines so you had to deduce
Original post by Leechayy
Same, rest in pieces:colonhash:

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Dw
Original post by Elcor
I said the force due to the field would oscillate so the cable would oscillate :s



No you don't, 0.01 goes into X-rays so 0.99 goes into heating the anode. For the next part you use the whole kinetic energy of 1 electron though, because that would produce the most energetic X-ray possible.

It would eventually fall to the ground, at first I wrote 'wobble' but then realised it would act with gravity making it fall

When it acts in opposite direction it would be in equilibrium

So eventually it'd get to surface of earth
Original post by Terry Tibbs
Need the A*s for Manchester Physics, think they'll probably let me in with one A* though.

Yeah, that's what Rachel needs too
Original post by Oraeng
This is exactly what I put! Why are people confusing things :frown:


Because they misinterpreted probably
Original post by Lunox
I also did this, but not sure if it is right!


you had to divide it by 1/60 as charge was only being dissipated for half the amount of time.

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