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# Edexcel Physics Unit 2 25th May 2012 Tweet

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• View Poll Results: How hard was the exam ?
 Extremely Easy 7 4.90%
 Easy 5 3.50%
 Average 31 21.68%
 Hard 62 43.36%
 Extremely hard 38 26.57%

1. Re: Edexcel Physics Unit 2 25th May 2012
uhhh seriously? the circuits question?
I just inputted random numbers into the formula:/
And in the table we had to fill in with the resistance, I thought the first value they put in should be 2R instead of R... :/
2. (Original post by xtron)
For the water droplet, the violet ray refracted less, because of the shorter wavelength, so it goes on top of the red ray.

But I made a stupid mistake by not showing it escaping the droplet, I just make it reflect back into the droplet. SO STUPID.
Violet actually refracts more.
You were spot on when you said it had a shorter wavelength but why refract less?
It has a shorter wavelength and that's precisely why violet refracts the most!
3. (Original post by bambi897064)
i got those answers, but not in that order.
I don't remember the order either but I think I got at least 3/4 correct if not all.
4. (Original post by PreciseUrination)
Very tough exam. Violet refracts less through the rain drop however buddy.

For the excited atoms question emitting Radiation, I discussed discrete energy levels resulting in distinct Frequencies of radiation.
However I mistakenly said that the Atom moves between the energy levels and not the Electrons of each atom.
How many marks do you think i'll be down?

For the beach question, I believe it's valid to discuss either a diffraction pattern as the rocks caused a "double slit" effect, or the reflected wave from the shore causing constructive and deconstructive interference.

For the thumbnail one, you had to divide the time by two, not multiply.

Doppler effect on the heart was a difficult question, I think you had to mention reflected pulses will undergo a doppler shift after coming in to contact with the heart.

Last page was the most difficult, full of trick questions. Resultant EMF was the difference between the two as the Cell's were in opposite directions to each other. Efficiency was about 80%, or 79.9% if you used 3 s.f.

I'm guessing at low grade boundaries, very unothordox questions, nothing that's come up before.
And why exactly does violet refract less?
Violet has the shortest wavelength and from my knowledge it's supposed to have the greatest refractive index.
http://www.physicsclassroom.com/class/refrn/u14l4a.cfm
5. Re: Edexcel Physics Unit 2 25th May 2012
(Original post by bambi897064)
do you think, if you had the wrong resistance in your table, you'd get follow through marks for the next question by using the smallest resistance of the four resistances in YOUR table?
Why would you pick the smallest of the R values when the question which combination would result in the most energy dissapated?
6. Re: Edexcel Physics Unit 2 25th May 2012
(Original post by 3.14159)
nope it is 2R, R/2 and 2R/3

i swear a few pages back you were boasting about how easy the paper was...
Yes, you're right. I got the exact same. Although, a lot of people got stuck on this question. I had to explain to over 20 people after the exam on how to do this question. They were all puzzled as to how the current can take the 'short-cut' and skip out the resistor...

For the second part, you then had to choose the lowest value right? V^2/R = Power, so R/2 is the state of switches?

Overall, I got the efficiency question wrong, the refracted raindrop and perhaps a few marks elsewhere... I'm predicting 65-70/80 for me Hopefully 120 UMS.
7. Re: Edexcel Physics Unit 2 25th May 2012
Still confused whether to multiply or divide by 2 in the pulse echo technique..Distance travelled was twice,ie sent and reflected, so 2D=sxt
8. Re: Edexcel Physics Unit 2 25th May 2012
sigh..
9. Re: Edexcel Physics Unit 2 25th May 2012
i wish i knew how many marks everything i did wrong was for oh dear oh dear
10. Re: Edexcel Physics Unit 2 25th May 2012
Guys does anyone know how edexcel calculates the UMS marks? How much would you thing 62/80 would be? PLease reply. Much appreciated!
11. Re: Edexcel Physics Unit 2 25th May 2012
(Original post by Respect1)
Guys does anyone know how edexcel calculates the UMS marks? How much would you thing 62/80 would be? PLease reply. Much appreciated!
That would depend on the grade boundaries. The lowest grade boundary for an A has been 45 and the highest is 59. Judging by the difficulty of the paper, you would definitely be well into an A - probably over 90% (108UMS)
12. Re: Edexcel Physics Unit 2 25th May 2012
(Original post by sabre2th1)
What paper was 48? And was that even harder then this?
I can't remember which paper, I just remember the grade boundary being stupidly low, and it was a LOT easier than this paper imo.

(Original post by jacksonrr24)
Still confused whether to multiply or divide by 2 in the pulse echo technique..Distance travelled was twice,ie sent and reflected, so 2D=sxt
You answered you're own question there... If it took t to cover 2D then it will take t/2 to cover D
13. Re: Edexcel Physics Unit 2 25th May 2012
(Original post by Sagacious)
Yes, you're right. I got the exact same. Although, a lot of people got stuck on this question. I had to explain to over 20 people after the exam on how to do this question. They were all puzzled as to how the current can take the 'short-cut' and skip out the resistor...

For the second part, you then had to choose the lowest value right? V^2/R = Power, so R/2 is the state of switches?

Overall, I got the efficiency question wrong, the refracted raindrop and perhaps a few marks elsewhere... I'm predicting 65-70/80 for me Hopefully 120 UMS.
yeah i chose R/2
14. Re: Edexcel Physics Unit 2 25th May 2012
Wasn't the pulse question about how LONG the pulse could be? so surely it's half so that it can actually get through the nail then come back out without interfering.

Also, I hated the last question, for the overall emf did you have to do the larger subtract the smaller voltage?

Did anyone get current by just doing V/R ?

For power outputted by the actual charger, since at the current, the voltage is 12 I just did 12 * 4.3, then for efficiency, subtracted the wasted power from the provided power and devided it by total and got 75%? but most people seem to have 80 or 10...

I think the other questions were alright though..
15. Re: Edexcel Physics Unit 2 25th May 2012
http://www.ndt.net/article/concrete/...#9...According to this we should have used 2xDistance=timex speed...i.e
2x.050x10^-3=2000xtime
time=5*10^-7s..Mathman is right
16. Re: Edexcel Physics Unit 2 25th May 2012
(Original post by Conan)
That would depend on the grade boundaries. The lowest grade boundary for an A has been 45 and the highest is 59. Judging by the difficulty of the paper, you would definitely be well into an A - probably over 90% (108UMS)
How many marks would gain you a UMS of 120 do you think? And thank you, and 62/80 for me is a prediction assuming no silly mistakes and what not. :P
17. Re: Edexcel Physics Unit 2 25th May 2012
(Original post by Count)
the question just asked to detect a heart beat and therefore i would assume detecting the doppler effect of moving blood would be enough (with a fancy diagram of course )
will i get marks or not?
18. Re: Edexcel Physics Unit 2 25th May 2012
(Original post by bambi897064)
i put as voltage is constant, lowest resistance has the greatest current flowing through the circuit, and P = IV so highest current is highest power and energy = power/time so will give the most energy in a given time
yeah I kept the same thing but i related P=I2R since I is high so power high.
19. Re: Edexcel Physics Unit 2 25th May 2012
can someone please tell me whether this is correct !!
for the emf question where they asked for current..
i used EMF= I(R+r)
WHICH meant that 15/0.7 =I
which gave me 21.4AMPS... is this wrong??
20. Re: Edexcel Physics Unit 2 25th May 2012
Did anyone else get 11.875 for the terminal potential difference question?
And 22.6V for the e.m.f. one?
And about 6.3 metres for the length?
Also, did anyone get about 5*10^-7 or something for the pulse echo question?
And did anyone get about 9mm for the diameter question?

I've probably got all these wrong but just wondering...
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