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

7 years ago
#241
I think comets can actually - not one of the main points but could do
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7 years ago
#242
(Original post by ChoYunEL)
I think some people here are confusing this with OCR Physics B..
Comet? That doesn't come up surely...
Page 216 2.5 3

By the end of this spread you must be able to:
-Describe comets
-Describe the formation of neutron stars and black holes

That won't take too long to do
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7 years ago
#243
(Original post by jam.wa)
time base - 50x10-6 s cm-1, pulse width - 2.4cm, ultrasound speed - 1.5 kms-1

- Work out the time difference between receiving pulse from the front of the head, and the back of the head first:

2.4 x 50x10-6 s cm-1 = 1.2 x 10-4 s

- Work out the difference in distance the echo has had to travel:

distance = speed x time; 1.5 x 10^3 x 1.2 x 10-4 = 0.18m

- Because this is the distance covered by the echo going to the back and then coming to the front again it's half this distance:

0.18/2 = 0.09m
For some reason I don't actually understand why its 2d....but I'll just memorise it. -_-
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7 years ago
#244
OCR A-level Spec
Candidates should be able to:
(b) describe the solar system in terms of the
Sun, planets, planetary satellites and comets;

Great... Well that hasn't come up yet... So heres to Comets on Tuesday!
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7 years ago
#245
(Original post by M_I)
For some reason I don't actually understand why its 2d....but I'll just memorise it. -_-
I know, it's quite confusing. I've had to just learn it.

When you look at those pulse diagrams, tell yourself, there's a pulse there because it's an echo, it's only been received because it's gone there AND come back. So, it's covered the same distance, twice.

I actually got over this hurdle after doing the exact same question as you.
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7 years ago
#246
Solutions to follow once the paper is done?
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7 years ago
#247
(Original post by mir3a)
Solutions to follow once the paper is done?
Those are always fun.
Seeing answers to the questions you thought you got right, are actually wrong.
Well, I guess it's okay when there's a moment of hope/happiness when everybody else plus you gets 3)c)iii) right.
However, I don't think it's much of a pay off when later on you are the only one to get 9)b)xvi) wrong.

In the end, I ALWAYS look anyway.
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7 years ago
#248
(Original post by mir3a)
Solutions to follow once the paper is done?
doubt it - only possible if someone miraciously remembers all of his/her answers - maybe if someone has access to the paper after the exam can post the solutions.
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7 years ago
#249
(Original post by jam.wa)
Those are always fun.
Seeing answers to the questions you thought you got right, are actually wrong.
Well, I guess it's okay when there's a moment of hope/happiness when everybody else plus you gets 3)c)iii) right.
However, I don't think it's much of a pay off when later on you are the only one to get 9)b)xvi) wrong.

In the end, I ALWAYS look anyway.
hahaha I know exactly what you mean

If only Arsey had a clone who could do physics
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7 years ago
#250
(Original post by anshul95)
doubt it - only possible if someone miraciously remembers all of his/her answers - maybe if someone has access to the paper after the exam can post the solutions.
How's S3 prep?
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7 years ago
#251
(Original post by anshul95)
doubt it - only possible if someone miraciously remembers all of his/her answers - maybe if someone has access to the paper after the exam can post the solutions.
Chemistry had the whole paper up on the same day... could happen.
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7 years ago
#252
(Original post by jam.wa)
Oh, the ones in the book? I know. They're ridiculous. But look at the dates, they're so old. In class we had to do ones older than us.

You know the ones that are so old the photocopier prints them diagonally across the page somehow?

I find if I write down the questions and answers of the ones I get wrong and memorize them, it will help me with some of the weirdo questions they like to throw into our exam.
The Nuclear/Space/Capacitors ones I can do

Medical/EMI are just something else.
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7 years ago
#253
(Original post by Martik)
Was getting confused about Lenz's law... as simple as it may be to learn.. it talks about the conservation of energy is applied therefore the emf induced is the opposite of the change that caused it... as energy was put in to move it against the resistance force?

Im guessing the resistance force is the force that the induced current will experience which is upward if you are moving the wired downward through the mag field ... so its kinda like a drag effect, as it only is in effect when motion of the wire is in effect.

this has been bugging me for a while...can you elaborate on what this resistive force is and how energy is conserved
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7 years ago
#254
I remember one hand is for induced current, EMI
I forgot what the other hand is for...
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7 years ago
#255
(Original post by ChoYunEL)
I remember one hand is for induced current, EMI
I forgot what the other hand is for...
Direction of magnetic field around wire, Right hand rule with thumb?
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7 years ago
#256
what do you guys predict will come up for this exam?
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7 years ago
#257
(Original post by Oh my Ms. Coffey)
Direction of magnetic field around wire, Right hand rule with thumb?
There's more than that...
I remember saying Force with the left thumb and then Motion with the right thumb but I don't remember why
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7 years ago
#258
(Original post by ChoYunEL)
There's more than that...
I remember saying Force with the left thumb and then Motion with the right thumb but I don't remember why
http://en.wikipedia.org/wiki/Right-hand_rule
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7 years ago
#259
The bottom line is that Fleming's left hand rule is used for electric motors, while Fleming's right hand rule is used for electric generators.

This is what I was looking for!

Left hand is for when it is already there,
Right hand is for induced.
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7 years ago
#260
(Original post by ChoYunEL)
The bottom line is that Fleming's left hand rule is used for electric motors, while Fleming's right hand rule is used for electric generators.

This is what I was looking for!

Left hand is for when it is already there,
Right hand is for induced.
Balls to that, I cant remember doing that and its not in my revision guide.
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