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EDEXCEL A2 Physics EXAM Unit 4 Physics On The Move 20th June 2016 (NOT I-A-L)

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Original post by KINGYusuf
The people who got 33% worked out the maximum distance, so the lowest to the highest, so the distance was twice what was necessary I think?

But the minimum distance that was necessary was 0.7mm


The question asked for the maximum percentage decrease so wouldn't you use the maximum change in distance?
Original post by 12amadaeus
The question asked for the maximum percentage decrease so wouldn't you use the maximum change in distance?


No because the normal charge is when the distance is at 3.5mm and your finding the maximum decrease from this
Original post by Jordan97
You had to find the charge difference when the plates were at 3.5mm and 4.2mm, not 2.8mm and 4.2mm


No, doing 2.8 and 4.2 gives you a larger percentage so surely that must be MAXIMUM percentage decrease???
Yeah the question asked you to find out the maximum decrease in % so you had to use Cmin (4.2mm) and compare it to the capacitance at 3.5mm, the correct answer was 16.6%

You can prove it now by calculating the percentage difference between 1/4.2 and 1/3.5 as k is a constant
(edited 7 years ago)
Original post by Salty carpet
Answers for the Linac 1 and 2 markers?


I said for the two marker: get longer as speed increases each times electrons are accelleraated across gap by electric field. Time spent in tubes must be constant as frequency of A.C constant. So by V=d/t tubes must be longer.
And tubes stay same size as KE converted to mass. Speed of electrons increases by less/ speed constant
All in all I thought it was a nice paper, and physics is my worst subject

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Original post by Jordan97
No because the normal charge is when the distance is at 3.5mm and your finding the maximum decrease from this

I see, it got 33% but I believe you are right.
Original post by sssmerch
No, doing 2.8 and 4.2 gives you a larger percentage so surely that must be MAXIMUM percentage decrease???


No, because at 2.8mm the charge has increased, youre trying to find the charge difference from 3.5mm as this is the normal, baseline charge that is required
Reply 108
Avatar for 1222fdf
1222fdf
Original post by lauren con
I got 80% too! doesn't seem like many people got the same though


I have got 20% instead, I though 0.7mm is the maximum you can splite so 80% will be left

But probably both won't be correct as many ppl in the post arguing 16.7 and 33 :frown:
Original post by Jordan97
No because the normal charge is when the distance is at 3.5mm and your finding the maximum decrease from this


the distance allowed between the plate is 3.5mm + or - 0.7mm. So the plate at one point can be at 4.2mm and still be in range, but from the it can go to 2.8mm and still be in range. so the maximum decrease that the plate can sustain within the range give would be 4.2mm-2.8mm rather than 3.5mm-2.8mm. but either way sounds like a suitable answer, the question was too vague.
Original post by Jordan97
No, because at 2.8mm the charge has increased, youre trying to find the charge difference from 3.5mm as this is the normal, baseline charge that is required


But what about if the distance goes from 2.8 to 4.2, in this case there has been a decrease in capacitance and so a decrease in charge I doubt you use the baseline
Original post by 1222fdf
I have got 20% instead, I though 0.7mm is the maximum you can splite so 80% will be left

But probably both won't be correct as many ppl in the post arguing 16.7 and 33 :frown:


It doesn't matter too much, we should get a few marks for using equations and its only one question out of the whole paper :smile:
Original post by Jordan97
No because the normal charge is when the distance is at 3.5mm and your finding the maximum decrease from this


You seem very certain. You sure you're not just backing your answer for the sake of it? I went for 16% and then changed my mind and doubled up for 33%. Tbh, the question was poorly worded and i doubt we'll know the real solution until the official markscheme comes out.
Either way, paper was very nice this year. Could be high grade boundaries though. Similar to last year?
(edited 7 years ago)
Reply 113
Avatar for klefki
klefki
3
Original post by Connorbwfc
I got 16.7% for the percentage charge decrease question.

20.4m for the radius of the path of the bike.
2.09ms^-1 for speed of bike.

Some multiple choice answers I remember:

1. Something to do with magnetic field causing circular motion
Area under graph = change in momentum
1/root(6)
Half charge on one of particles
Anti-up Down
0.024N


same for all
Original post by AA10743
You seem very certain. You sure you're not just backing your answer for the sake of it. I went for 16% and then changed my mind and doubled up for 33%. Tbh, the question was poorly worded and i doubt we'll know the real solution until the official markscheme comes out.
Either way, paper was very nice this year. Could be high grade boundaries though. Similar to last year?


Because the question said "The distance between the plates is 3.5mm" therefore you use that
Original post by Jordan97
Because the question said "The distance between the plates is 3.5mm" therefore you use that


It also said 0.7mm from that position. Not sure on exact phrasing but it definitely implied either way. This is the problem with poorly worded questions. I definitely agree with what you're saying and I'm not backing my answer over yours. Very much a lottery with this one
What did people write for 12 d with the hydrogen ion?
Original post by AA10743
You seem very certain. You sure you're not just backing your answer for the sake of it? I went for 16% and then changed my mind and doubled up for 33%. Tbh, the question was poorly worded and i doubt we'll know the real solution until the official markscheme comes out.
Either way, paper was very nice this year. Could be high grade boundaries though. Similar to last year?


i think the grade boundaries will be similar to last year. last year it was 62 for an A, so i don't think it would be less than 62 for an A this year.
Reply 118
Avatar for klefki
klefki
3
Original post by CallMeArchie
What did people write for 12 d with the hydrogen ion?


I put that it had no momentum? Only reason there'd be no track is if it didn't move or it decayed but I don't think protons decay, so I just went with 0 velocity
What did you guys put for the question about the values on the speedometer?

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