# June 2011 G485-Fields, Particles and Frontiers of PhysicsWatch

7 years ago
#741
What would be a good answer to this question:

Why does the calculated age of the Universe depend on its density?
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7 years ago
#742
(Original post by ChoYunEL)
A-Scan - Depth scan, looking at the time the crystal responds. Using depth scan, can find dimension of... blah
B-Scan - using an array of scanners to create a 2D/3D image. The echoes received determines the dimension etc .
So A uses 2d=ct where c is the speed in the material. B scan uses the same process from different angles to create a 2D/3D image.
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7 years ago
#743
(Original post by LBenjamin93)
the radiation is at a temperature of 3K, and is a remnant of the heat radiation which was spread out in the Universe shortly after the big bang. it's cooled to this temperature because the Universe has been expanding, showing that the Universe isnt static, therefore supporting the Big Bang Model
Thanks.
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7 years ago
#744
(Original post by ChoYunEL)

Simply put,
They are similar, Static involves charges, Magnetic involves movement
Thanks.
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7 years ago
#745
(Original post by M_I)
What would be a good answer to this question:

Why does the calculated age of the Universe depend on its density?
Very good question, I am not sure. I could only show it using the equations and substituting age in for 1/h0.

My revision guide doesnt really give an answer.
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7 years ago
#746
(Original post by Oh my Ms. Coffey)
So A uses 2d=ct where c is the speed in the material. B scan uses the same process from different angles to create a 2D/3D image.
Yes, but an B-Scan is not lots of A-Scans. A B-Scan is an array of sensors in different angles.
An A-Scan is just range.
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7 years ago
#747
(Original post by Oh my Ms. Coffey)
Very good question, I am not sure. I could only show it using the equations and substituting age in for 1/h0.
What equations would you use?
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7 years ago
#748
(Original post by Oh my Ms. Coffey)
Can you define acoustic impedance using the equation and elaborating on the terms?
Z=pc, Acoustic Impedance = Density of material x speed of ultrasound in material.
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7 years ago
#749
(Original post by M_I)
What would be a good answer to this question:

Why does the calculated age of the Universe depend on its density?

Rearrange the equation Pc = 3H0^2 / 8(pi)G to make H0 the subject.

Invert the equation to give 1/H0 = sqroot( 3 / Pc x 8(pi)G)

Then see what the effect Pc has on the age?

That would be my guess...
0
7 years ago
#750
(Original post by M_I)
What equations would you use?
(8piGp/3)^-0.5 = Age I think.

p = Density
G = Newtons gravitational constant
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7 years ago
#751
(Original post by ChoYunEL)
Z=pc, Acoustic Impedance = Density of material x speed of ultrasound in material.
Hello Yung x
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7 years ago
#752
(Original post by CoffeeStinks)
OOOOHHHHH NOOOOO!

And it would probably be just my luck for them to ask a 15 mark question on it. Â¬_Â¬.
The only thing is I think everyone would find that hard. And it's not really a test of how good you are at Physics which is what annoys me.
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7 years ago
#753
Gaah...

The only thing left to do is to read through the book before bed...
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7 years ago
#754
More hard questions.
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7 years ago
#755
In the paper you get given...
65 km sâ€“1 Mpcâ€“1. One parsec = 3.1 Ã— 10^16 m.

65000 / (3.1x10^16 * 1x10^6) Which translate to...
65000 / 3.1x10^22 = 2.10 x 10^-18 s-1

A ms-1 / Bm = Cs-1
Therefore, the Age of the universe in seconds, is 1/Hubble Constant
Which is in this example,
1/(2.10x10^-18) = 4.76x10^17s
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7 years ago
#756
(Original post by Lengalicious)
judging by what didnt come up in the last 2011 jan paper, im guessing there will be a question utilising the equation f ' = c/(c-2v) x f in ultrasound, in med imaging there will probz be a question on PET scan or gamma camera as MRI was in last paper,
you don't need to know that formula
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7 years ago
#757
R.I.P Papworth
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7 years ago
#758
is it me or do you think this exam will contain a lot of modules 1 and 2 in it.
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7 years ago
#759
(Original post by susan23)
is it me or do you think this exam will contain a lot of modules 1 and 2 in it.
Unit 1, well they had some unit 1 projectiles in the first mock paper for electric fields so I dont think so maybe some density. Unit 2 is much more likely.
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7 years ago
#760
(Original post by M_I)
What would be a good answer to this question:

Why does the calculated age of the Universe depend on its density?
Po=3Ho/8(pi)G

Age of uni=1/Ho ,so Ho=1/age of uni

sub in

Po=3/8(pi)G*age of uni

so greater Po, lower age of uni.

i think anyway lol
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