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What's Chico Time Precious?
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#81
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#81
Not really all that bad, i think it was harsh but fair, some hard bits but generally ok.

Grade boundaries probably be standard, ie not go up or down dramatically?
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iiikewldude
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#82
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(Original post by Resonance)
It's worth 20% of the A-level.
are you serious? i thought it was only 16.7% anymore than that and i am screwed.

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InterCity125
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#83
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I found it realy hard.
for the graph it was a sin curve - we did it in class
for the cadmium decay i got 9 years - worked it though to get the number of nuclei for 15W and then calcuulated this as a 100% of the original and ehcen deduced the fraction of a half life -could be wrong here.
I messed up on that cable question - didn't correctly draw either of the fields
completly forgot part of the anlogy question - only could do half
made a few mistakes on question 1 about proving that formula
got the TV thing right though.
I need to get 135UMS across 5 and 6 - hopefuly the grade boundaries will go up to allow this.
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crana
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#84
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#84
(Original post by iiikewldude)
are you serious? i thought it was only 16.7% anymore than that and i am screwed.
Yeah, 20%


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Mysticmin
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#85
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#85
I got 7.5 years for that decay question.
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S1M
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#86
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#86
(Original post by Kabeer)
CRTs scan from left to right :eek: , whaa ! this wasnt in any of the physics modules syllabus, that is a bit unfair how do they expect us to know it!

Unless of course we watched a tv program caled the history of television 8 years ago
actually i dont think this is right... my tv isnt a crt(plasma )... and i can notice this problem (several cms to the right sometimes)... my tv progressively displays all the pixels all at once... but i still experience the shadow! so i think the history of television was wrong
EDIT: i use an arial on the tv sometimes too

(Original post by Mysticmin)
I got 7.5 years for that decay question.
I got this too as did many other people... we must be right
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Mysticmin
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#87
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#87
(Original post by S1M)
I got this too as did many other people... we must be right
Yes, I sincerely hope so
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InterCity125
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#88
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#88
(Original post by S1M)
actually i dont think this is right... my tv isnt a crt(plasma )... and i can notice this problem (several cms to the right sometimes)... my tv progressively displays all the pixels all at once... but i still experience the shadow! so i think the history of television was wrong
I got this too as did many other people... we must be right
The TV is to do with the fact that the reflected image lags the main one. Plot the graph of a leading and laging waves, and since the time base starts for 0 it is towards the right.
I must have got the deacy wrong - will get the method but to the ans - 2/3 ain't bad i suppose.

BTW - what would the raw % to get a B be for the paper - I'm thinking about 64%.
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Mysticmin
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#89
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It's about 80% for an A, 70% for a B even in raw mark status judging by the june 2003 boundaries someone posted up here.
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qqqwwweee
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#90
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Where did you sketch your graphs? In the answer book or on the graph paper?
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Emma Louise
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#91
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#91
... we didn't get graph paper.
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qqqwwweee
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#92
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(Original post by crana)
I really messed up that paper..

For the shifting to the right on the TV screen, because the displacement for just one reflection was small, I put that possibly the signal could reflect multiple times so that the displacement would be larger and noticeable, however it would be faint as only a small proportion of the energy in the original signal would be reflected several times..

did anyone else get this?
I dont think the further reflections are significant as the intensity keeps decreasing.

(Original post by crana)
For differences in radioative source/VdG, I put (but largely invented):
- VdG can produce different energies as desired/source has fixed energies
-VdG can emit the particles in one direction in a "beam" - source chucks them out randomly
- source's activity variable as random and also activity decreases with time - VdG has a more constant output
-VdG can produce higher-energy particles
?!
the question asked the difference between the BEAMs of the 2MeV ions and the 2MeV alpha particles. So only the second point answers it.
The beam from VDG is acclerated thru cylindrical electrodes or with a small opening, so it is more uni-directional. But a beam from the alpha source travels in all directions.
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qqqwwweee
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#93
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(Original post by Emma Louise)
... we didn't get graph paper.
we were given one at the start, but I didnt use. Because they were only "sketches" not plotting
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qqqwwweee
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#94
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(Original post by Camford)
I think the electric field is a radio field. The field outside the cable is in one direction; the field inside the cable in another direction. Don't know whether the copper wire is +ve or -ve, they probably would take a mark off me for that one. Then again, how was I to know which is positive.
I think in this case it can be assumed that there is no field outside because the charge on the sheath are induced by that in the wire and they are so closer togther that any stray capacitance does not matter.

(Original post by Camford)
For the magnetic field inside the cable I said something about the fields close to the wire and the sheath being in opposite directions. and there will be a region where there's no apparent fields. The field outside the cable is main influnced by the current in the sheath.

God I hate that paper.
I put a strengthened field inside and a weakened outside. The field outside is not cancelled.
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rich_greeny
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#95
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the question about the inelastic scattering i said about how in the gold leaf experiment, electrons are fired, not helium atoms, hence with the RBS scattering, there is a higher likelihood of a collision, where as in inelastic scattering, there is a much slimmer chance of there being a collision. Dunno if that counts for anything?!

As for that decay question, didn't have a clue. Tried to run A=lamda*N and power together, but just couldn't find the link between them. That pissed me off.


Other than that, i thought the paper wasn't too bad. Hope i've got about 60% on it, i need a B overall.

Oh also, i forgot to go back to the electric and magnetic field diagrams around the coaxial cable, told myself i'd come back to it, and forgot. woops.
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qqqwwweee
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#96
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#96
(Original post by Mysticmin)
It's about 80% for an A, 70% for a B even in raw mark status judging by the june 2003 boundaries someone posted up here.
Refer to this post
76.25% for an A and 68.75% for a B

They should be lower for this year paper
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crana
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#97
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(Original post by rich_greeny)
the question about the inelastic scattering i said about how in the gold leaf experiment, electrons are fired, not helium atoms, hence with the RBS scattering, there is a higher likelihood of a collision, where as in inelastic scattering, there is a much slimmer chance of there being a collision. Dunno if that counts for anything?!
Didn't Rutherford use alpha particles in the gold leaf expt? Unless I am mistaking what you mean..

Why would there be a lower chance of collision? Granted, electrons are smaller, but you have to make He nuclei (not atoms) go very fast to get them to hit a nucleus - as they have a 2+ charge.
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crana
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#98
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(Original post by keisiuho)
I dont think the further reflections are significant as the intensity keeps decreasing.
.
Yeah, I said that was why it was so faint..

(Original post by keisiuho)
the question asked the difference between the BEAMs of the 2MeV ions and the 2MeV alpha particles. So only the second point answers it.
The beam from VDG is acclerated thru cylindrical electrodes or with a small opening, so it is more uni-directional. But a beam from the alpha source travels in all directions.
Does anyone remember exactly what the question said?
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Resonance
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#99
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Dang, I just realised that for the decay question, my answer of 0.75 years was probably due to a stupid standard form error!!!!! Hopefully I got the majority of the marks for that.

Here's hoping the grade boundaries are pretty low.
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S1M
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#100
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(Original post by Resonance)
Dang, I just realised that for the decay question, my answer of 0.75 years was probably due to a stupid standard form error!!!!! Hopefully I got the majority of the marks for that.

Here's hoping the grade boundaries are pretty low.
i thought most people got 7.47 years...
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