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# The Physics PHYA2 thread! 5th June 2013 Watch

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1. (Original post by StalkeR47)
so, what is the number of blocks you got?

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2. (Original post by Felix Ivers)
When describing an experiment looking at stress and strain, is it okay to assume gravity = 10 newtons per kilogram? So that when you add masses on, you are adding a 100g mass which is a 1N force?
Sorry if I'm not being clear.

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I have seen some mark schemes accepting 10ms-2 for the gravity. However, it is more safer to use 9.81 or just 9.8ms-2 for the gravity.
3. how do you use a mirror to eliminate parallax error when reading off a ruler?
4. (Original post by Jimmy20002012)

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Wow great! That was exactly what I estimated. So, find the area of 1 block and times it by 38. Is that ok or do are you still stuck? If yes then I will give you the straight solution. Oh forget it. I will give you the solution now since I am going to sleep in a bit. The area of 1 block is, 0.5x10^-3 times 0.2x10^8. You get 10000Jm^-3. so, times 10000 by 38 and you get 380000Jm^-3.
5. (Original post by Jack93o)
page 183 of nelson thornes textbook

in the green text box:

''phase difference between two particles is equal to m(pi), where m is the number of nodes between the particles''

but remember if its an even number of pi, then the two particles are effectively in phase, meaning the phase difference between them is zero

THIS ONLY APPLIES TO STATIONARY WAVES!!!!!

its different for progressive waves
Thank you good sir
6. Yo could anyone help me out with question 6b on jan 12, how would the ray leaving the prism look like ?! it says away from the normal! kinda confused! THANKS!
7. (Original post by StalkeR47)
I have seen some mark schemes accepting 10ms-2 for the gravity. However, it is more safer to use 9.81 or just 9.8ms-2 for the gravity.
So that means when you want to add a 100g mass you're adding a 0.981N force? Then if you draw a graph of force against extension your independent variable will be going up by 0.981 each time? That just seems weird, surely it would make much more sense to increase the force by 1N at a time by adding a 100g mass?

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8. (Original post by Jack93o)
page 183 of nelson thornes textbook

in the green text box:

''phase difference between two particles is equal to m(pi), where m is the number of nodes between the particles''

but remember if its an even number of pi, then the two particles are effectively in phase, meaning the phase difference between them is zero

THIS ONLY APPLIES TO STATIONARY WAVES!!!!!

its different for progressive waves
how do u know if the points are in phase or antiphase?
9. (Original post by StalkeR47)
Wow great! That was exactly what I estimated. So, find the area of 1 block and times it by 38. Is that ok or do are you still stuck? If yes then I will give you the straight solution. Oh forget it. I will give you the solution now since I am going to sleep in a bit. The area of 1 block is, 0.5x10^-3 times 0.2x10^8. You get 10000Jm^-3. so, times 10000 by 38 and you get 380000Jm^-3.
Thanks again Good luck I am sure you will smash this exam and get full ums

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10. (Original post by Felix Ivers)
So that means when you want to add a 100g mass you're adding a 0.981N force? Then if you draw a graph of force against extension your independent variable will be going up by 0.981 each time? That just seems weird, surely it would make much more sense to increase the force by 1N at a time by adding a 100g mass?

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Alright! For a graph, you can use 10ms-2 making it more easier for you to do. so, 100g is ok.
11. (Original post by StalkeR47)
Alright! For a graph, you can use 10ms-2 making it more easier for you to do. so, 100g is ok.
Aha okay cheers

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12. (Original post by Jimmy20002012)
Thanks again Good luck I am sure you will smash this exam and get full ums

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Thanks. I also hope but still I am a bit scared as usual. And, You are definitely going to do really well. You can easily get an A since you are a hard working guy and you have a sound knowledge of physics. Good luck my friend!
13. (Original post by Felix Ivers)
Aha okay cheers

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No probs. and Good luck to you m8.
14. Guys...

w = lamda D / s

^ Is this for single slits

dsing() = n lamda

^ & this is for double slits & diffraction gratings

I've probably got this wrong... so could anyone clear up my confusion please

15. Is the fringe spacing the distance between the centre of a maximum to the centre next maximum along or the centre of a maximum to the centre minimum next to it?

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16. (Original post by StalkeR47)
No probs. and Good luck to you m8.
You too!

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17. (Original post by Felix Ivers)
So that means when you want to add a 100g mass you're adding a 0.981N force? Then if you draw a graph of force against extension your independent variable will be going up by 0.981 each time? That just seems weird, surely it would make much more sense to increase the force by 1N at a time by adding a 100g mass?

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Or you could say add weights equal to 1N each time?

Remember to say add at least 8
18. (Original post by Boop.)
how do u know if the points are in phase or antiphase?
points are in phase if they;re separated by an even number of nodes (you know what nodes are, right?)

i.e, theres 2 nodes between two points, so thats 2*(pi) = 360 degrees, which is basically zero phase difference

and points are antiphase if they're separated by an odd number of nodes

but this rule only applies to stationary waves

for progressive waves, to find the phase difference between two points, you need to find the distance between them, divide this by the wave length, and then multiply by 2(pi)
19. good luck to everyone for tomorrow, i'm resitting this exam and hoping for atleast 110 ums.

hopefully its a nice straightforward paper with a nice 6 marker.
20. Hi every one for May 2012
Q.6 a) ii) state the phase relationship between
X and Y
and
X and Z

why is it for X and Y - pi radians and for X and Z - 2pi radians I mean they dont look in anti phase and in phase, respectively.

I thought for X and Y they are 3pi over 2 rad cos its not exactly pi radians difference... from first impressions

Thanks

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