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OCR Advancing Physics G492 ~5 June 2013~

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Thank you! That's a big help, I always get stuck on questions about improving experiments. You must have been over the moon when you saw this experiment on the pre release :smile:

Well Im actually in year 13 and cant really remember much of the experiment but yeah pretty pleased although dont really see what could be asked about the 3rd part :/ but no worries message me if you need help!

Reply 61

Joynzer

Hi could someone please give me a hand with the graph questions which always appear at the very start of the paper? Is there an actual method or is it guess work? Thanks :l I'm really stuck!

Reply 62

upthegunners

Original post by Joynzer

Hi could someone please give me a hand with the graph questions which always appear at the very start of the paper? Is there an actual method or is it guess work? Thanks :l I'm really stuck!

you have to look at the equation involving the 2 given variables

eg: if it's a speed-time graph it'll be a

y=mx+c

graph as the equation linking the variables speed and time is linear.

Reply 63

Bloxorus

The pre release says that the equation v^2=u^2+2as can be used to determine the value for g.
Would you simply find a using the equation for each angle then because a=gsintheta you could plot a graph with a on the y axis and sintheta on the x axis and the gradient would be g? Is this a method they would accept?

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Reply 64

The Monk

Does anyone know whats in the formula booklet ?

Reply 65

upthegunners

Original post by The Monk

Does anyone know whats in the formula booklet ?

Formulas? I think. Not sure though.

Reply 66

m00c0w

Which formulas do we need to know that aren't in the formula booklet?

Reply 67

Bloxorus

Original post by m00c0w

Which formulas do we need to know that aren't in the formula booklet?

Well the main formula that springs to mind is the x=Llambda/d to calculate fringe spacing. There are a few others such as kinetic energy (E=1/2mv^2) and F=ma. I think thats pretty much it, but there are probably a few others but most likely very generic and you'll probably know them by heart already.

Reply 68

ArchieL

Original post by m00c0w

Which formulas do we need to know that aren't in the formula booklet?

These are the one's I'm thinking (Some are simple, I know):
Double slit experiment: S=(lambda*L)/w (x/L) = tan(Theta) ≈ sin(Theta) ≈ Theta
Single aperture: For a min: dsin(theta) = lambda
Beam width: Theta(in radians)= lambda/d
Misc: W=fd, P=Fv, P ɑ A^2, Intensity ɑ A^2
Sensitivity = (change of output)/(change of input)
Resolution = Smallest observable change
Accuracy = (resolution)/(sensitivity)

Let me know if nothing makes sense :smile:

Reply 69

ArchieL

Also some questions from my physics dept:
http://puu.sh/38deP.jpg
http://puu.sh/38dfX.jpg
http://puu.sh/38dgC.jpg

(Sorry for low-res, my internet is appalling, I'll put up the general notes in one sec)

IMG_1470.jpg511.2KB

Reply 70

m00c0w

Original post by ArchieL

We've already got lambda=dsin(theta), W=fx, P=fv, but thanks for the others
How would you calculate resolution? What is beam width? I don't remember being taught it nor seeing it in past papers.
So the main one we really need to know is S=(Lambda*L)/w (which is S and which is w?)

Thanks again!

Reply 71

m00c0w

Original post by Bloxorus

Thank you! Could you remind me which is x, and which is d? I always forget! Another one I remembered is Gravitational Potential energy=mgh.

Reply 72

Smidge

Original post by walkers38

What did you guys get in G493? The practical. I got 17/20 :smile:

19/20, 29/30 overall

Reply 73

m00c0w

I got 20/20 and either 8 or 9/10 (don't know why it was so low, seeing as I had to describe some pretty high level physics)

Reply 74

ArchieL

Original post by m00c0w

Haha, sorry for that- it'll teach me to reply in a hurry!

In the case of the graph we're given, I'm guessing it's 4mV/Degree (smallest observable change => one square)

'Beam' width is the estimated spread of the fringes from the single slit experiment. It's basically a boil-down of din(theta)=lambda, as sin(theta) = theta at small angles. It's easy to do quick calculations on and have used it in most past papers I've done.

Finally, for a two-slit experiment:
Lambda = wavelength of coherent source
L = Distance of screen from aperture
W = slit width (d in other formula)
S = fringe separation

Lambda = (ws)/L
=> s = (Lambda*L)/W

So:
Increasing wavelength increases s
Increasing L increases s
Increasing W decreases s

Also make sure you remember the key energy equations and stuff (though you should know them already!):
E = 1/2mv^2 = mgh = Fd
These come up quite a bit, and can confuse!

(edited 10 years ago)

Reply 75

Bloxorus

Original post by m00c0w

Thank you! Could you remind me which is x, and which is d? I always forget! Another one I remembered is Gravitational Potential energy=mgh.

X is the fringe spacing on the screen and d is the slit spacing. Yeah GPE is another, theres a few more like that but they are very basic i.e. sensitivity=gradient of line etc.

Reply 76

ArchieL

One thing I haven't seen in a little while is a question about standing waves in pipes? Please correct me if I'm wrong, but:

Closed at both ends: Nodes at both ends.
Open at one end: Antinode at open end, node at closed end.
Open at both ends: Antinode at both ends.

Can we just work from there?