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# OCR PHYSICS B G494~ 11th June 2015 AM ~ A2 Physics watch

1. (Original post by Lissy14)
****
I put sound
I don't think it can be sound because it was in space so there are no air particle. I put heat
2. (Original post by SublimeOrangeUK)
What did people put for the equipotential lines?
The sideways snowman shaped thing
(Not the 8 or the straight lines)
3. (Original post by ZestyX0r)
Okay, I get the theory behind it, but the only value for density it gave you was for density of surface rocks on Earth? typo, or am I just misinterpreting what that means?
yeah, the assumption you had to make was that the density of the surface rocks = the average density of the earth, which was the answer to the later question about why the value for G was wrong (also that the equatorial radius is not the same as the earth's radius)
4. (Original post by ryanWales)
I don't think it can be sound because it was in space so there are no air particle. I put heat
I put heat

For the question about why G is different could we say the methods are now more precise?

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5. (Original post by ryanWales)
I don't think it can be sound because it was in space so there are no air particle. I put heat
Yeah
6. (Original post by Mutleybm1996)
Could we say that the methods of measurement are more accurate?
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What question is this for?

(Original post by ZestyX0r)
Okay, I get the theory behind it, but the only value for density it gave you was for density of surface rocks on Earth? typo, or am I just misinterpreting what that means?
No you're right, and you were supposed to just use that as the average density of the Earth itself. That's the reason why the value of G calculate at the end was wrong.

(Original post by urz13)
I didn't calculate the final voltage - I just did Q=0.12C (whatever C was), then dQ/dt = 0.94uA I think 0.94 is about right as later in the question it said it was originally 1uA, or something!
Ah fe. Everyone seems to have gotten that so it must be correct - I'll at least only drop 1 mark because I wrote out the formula, must've just messed up when subbing in values.

(Original post by rapunzelsa)
why is kinetic energy not conserved in the collision?? i know it's probably something really easy but i thought it can't be lost to sound because it said something about being in space :-(
Yeah as other people have said, heat or sound upon collision.
EDIT: Oh yeah I noticed that it was in space so thought 'can't be friction then'. Still I then went and wrote down sound energy, oh dear.
7. (Original post by Rhetorical Hips)
What question is this for?

No you're right, and you were supposed to just use that as the average density of the Earth itself. That's the reason why the value of G calculate at the end was wrong.

Ah fe. Everyone seems to have gotten that so it must be correct - I'll at least only drop 1 mark because I wrote out the formula, must've just messed up when subbing in values.

Yeah as other people have said, heat or sound upon collision.
EDIT: Oh yeah I noticed that it was in space so thought 'can't be friction then'. Still I then went and wrote down sound energy, oh dear.
For the G question

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8. (Original post by urz13)
Horrible paper for me, I don't think I did well. I've got an A* on virtually all of the past papers but that was massively frustrating. I got G as something x10-16 and 0.45Hz, ugh
I got G as that initially but changed it to the correct one, you would have used r as the radius of the earth from the previous page as opposed to r from r=ct/2
9. (Original post by asdfghi)
I got G as that initially but changed it to the correct one, you would have used r as the radius of the earth from the previous page as opposed to r from r=ct/2
I forgot to add the radius of the Earth. How many marks do you think I'll loose for that?
10. (Original post by asdfghi)
I got G as that initially but changed it to the correct one, you would have used r as the radius of the earth from the previous page as opposed to r from r=ct/2
Was it something x10^-10???

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11. (Original post by Rhetorical Hips)
What question is this for?

No you're right, and you were supposed to just use that as the average density of the Earth itself. That's the reason why the value of G calculate at the end was wrong.
poo :P
oh well 3 marks gone
12. [QUOTE=Mutleybm1996;56878533]Was it something x10^-10???

Yeah like 1.22x10^-10..some found it to be 1.28x10^-10 because of the extra distance of the earth...but it was only a two marker
13. What did people get for the rate one? Where it said rate of molecules colliding on a surface area of 0.56 or something.
I got like 1.2- x10^24 or something very big

It was the 4 marker one
14. (Original post by champion1)
What did people get for the rate one? Where it said rate of molecules colliding on a surface area of 0.56 or something.
I got like 1.2- x10^24 or something very big
I got ^23 or ^27 or something

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15. (Original post by ryanWales)
I forgot to add the radius of the Earth. How many marks do you think I'll loose for that?
I didn't add the radius of the Earth as it specifically implied r=2ct/d and also because I added the radius of the Earth in a past paper and to the right it said reject/ignore if radius of the Earth is added so a similar question.

Hope the same applies to this, it would seem that it should.
16. (Original post by Mutleybm1996)
I got ^23 or ^27 or something

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What about for the assumption? I put something like we assume all momentum is transferred to the area.
17. Wait so some people added the radius of the Earth to the distance between the Earth and Moon when calculating G? I thought that 'r' in that equation only represents the distance between the Moon and the Earth's surface...

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18. (Original post by Mutleybm1996)
I got ^23 or ^27 or something

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I also got some ^27. I think it was rate of change of momentum on face of box or w/e = 10^5 * 0.56 = 56000 N per s

Then divide by the rate of change of momentum of ONE particle which was like 512 * 2.5x10^-26 or something (can't remember the mass of the particle)

And that gave me an answer of something ^27. Some people got ^23 idk which one it correct.
19. (Original post by champion1)
What about for the assumption? I put something like we assume all momentum is transferred to the area.
I said elastic collisions, someone I know put forces were instantaneous which also sounds good.

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20. (Original post by Rhetorical Hips)
Wait so some people added the radius of the Earth to the distance between the Earth and Moon when calculating G? I thought that 'r' in that equation only represents the distance between the Moon and the Earth's surface...

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Pretty sure that's wrong
G was close, but not the same

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