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# A2 (Edexcel) Physics Unit 4 & 5 6PH08 June 2012

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1. Question 1 to 16 was a breeze. Question 17 and 18 effed me over...

Does anyone remember what direction L was for question 17? (the question with the fluorescent screen and electron being fired) thanks.
2. (Original post by Freddy12345)
well for that question what i did was first times the mass of the propellent by the speed so we got that momentum. Then I tried to think it out, so it was in space and the type of set up was an explosion, so I said that the momentum of the ship and the propellent must = 0. so taking the momentum of the ship as negative then dividing by the mass, I got the answer 8.02m/s so I said the predicition was pretty accurate, but I am not convinced I am right.
😓
I got 8.03 for that question, I removed the mass of the released fuel before I found the velocity

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3. Why does the nucleus has surplus energy after the emission of a B- particle?
4. Can anyone help me understand how to calculate the mass deficit of an atom?

There is a worked example in page 139 of the Miles Hudson book of a proton-proton chain reaction.

I cannot understand how they calculated the mass of the He nucleus to be 4.002602u!
Didnt like probing the formula of the tan theta question--had to work myself backwards
For that same question the last part--why was the equation wrong?(2 marks) I didnt have time to put anything as I left for the end but didnt have extra time ahhh!
I think it was because the F=BeV was calculating a centripetal force where as the F=EQ wasn't (something like that) I didn't have time to answer it as well but I thought of that possibility when I left the exam room (damn!).

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6. What did every one get as their momentum for the Nutrino particle in the last question from the unit 4 paper, if you can remember it that is? I got 110 MeV/c (roughly).
7. (Original post by steve10005)
What did every one get as their momentum for the Nutrino particle in the last question from the unit 4 paper, if you can remember it that is? I got 110 MeV/c (roughly).
I got 107 but that was only 1 mark
I got 107 but that was only 1 mark
Yh unfortunately, trying to draw the vector diagram with the correct angles was quite time consuming for me, that was about 2 marks. :/ But at least someone got almost the same as me :P
9. In question 17 with the florescent screen, there was a question about how Thompson would of measured the angle of deflection. I said he could of used trigonometry to get a rough measurement but then I reaslised the screen was curved. :O
10. has anyone got Unit 5 papers, marking schemes and ER all in one one folder. It's taking ages trying to find them individually.
11. Hey can someone help me out with the answer to this?

The magnitude of the fractional change in frequency, Af / f, produced in the Doppler
effect depends upon
A the relative velocity of the source and the observer.
B the wavelength of the radiation being emitted by the source.
C whether it is the source or the observer that is moving.
D whether the source and observer are approaching or receding.
12. (Original post by poopypie)
Hey can someone help me out with the answer to this?

The magnitude of the fractional change in frequency, Af / f, produced in the Doppler
effect depends upon
A the relative velocity of the source and the observer.
B the wavelength of the radiation being emitted by the source.
C whether it is the source or the observer that is moving.
D whether the source and observer are approaching or receding.
I think its A
I think its A
Yea you're right, but I don't understand why. I thought it would be D because that would shift the wavelength and hence the frequency of waves, and the magnitude would change...
14. (Original post by poopypie)
Yea you're right, but I don't understand why. I thought it would be D because that would shift the wavelength and hence the frequency of waves, and the magnitude would change...
Relatively velocity affects the size of the frequency change. Greater the relative velocity, greater the change in observed frequency.

Whether the galaxy is moving away or towards us affects whether the frequency increases or decreases (or to which end it shifts - red or blue). If it is moving away, frequency increases. If it is moving closer, frequency decreases.
15. (Original post by steve10005)
Yh unfortunately, trying to draw the vector diagram with the correct angles was quite time consuming for me, that was about 2 marks. :/ But at least someone got almost the same as me :P
Yeah for that question I just guesstimated, I didnt draw any angles but I got more or less the answer. Alotugh I knew we had to use a protector, so I thought its 2 marks and it will use my time up so might aswell just estimate how it was
16. does anyone have any Idea what might come up tommorow
17. (Original post by steve10005)
I think it was because the F=BeV was calculating a centripetal force where as the F=EQ wasn't (something like that) I didn't have time to answer it as well but I thought of that possibility when I left the exam room (damn!).

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Wouldn't it be because F=Bev gives you the force a charged particle feels in a "magnetic field" where as F=EQ would give you the force a charged particle will feel in an electric field?
18. (Original post by elkana)
does anyone have any Idea what might come up tommorow
Unit 5 Physics A2 Level Exam will come up tommorow.
Gas Laws,Nuclear Decay,Oscillation,Astrophysics and Cosmology are 100 per cent likely to come up!
19. (Original post by Parthenon93)
Relatively velocity affects the size of the frequency change. Greater the relative velocity, greater the change in observed frequency.

Whether the galaxy is moving away or towards us affects whether the frequency increases or decreases (or to which end it shifts - red or blue). If it is moving away, frequency increases. If it is moving closer, frequency decreases.
Oh alright, I get it now! Thanks!!!

by the way if an object is moving away, the frequency decreases and vice versa.
20. (Original post by osake)
Wouldn't it be because F=Bev gives you the force a charged particle feels in a "magnetic field" where as F=EQ would give you the force a charged particle will feel in an electric field?
Yes but in passage before the question it said Thompson changed the electric field to a magnetic one so then he changed the equation to include F=Bev. You had to show why he done it but the next one asked why it was wrong.

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