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Author Topic: CIE physics paper 2  (Read 11799 times)

Offline Hwa1

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Re: CIE physics paper 2
« Reply #90 on: November 16, 2009, 07:42:13 pm »
well we did variant 2
and the phase difrnce was 180 degree or pi/2  (antiphase)
and the amplitude was just A, same as the other point o.O
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Offline Dooraven

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Re: CIE physics paper 2
« Reply #91 on: November 16, 2009, 10:54:04 pm »
Well its either A or -A for sure.
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Offline vince_24

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Re: CIE physics paper 2
« Reply #92 on: November 17, 2009, 01:40:14 am »
Amplitude is the maximum displacement. Antinode is place of maximum displacement. The point wasn't at an antinode so how exactly would the amplitude be A? Please enlighten me. Thanks.
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Offline kratos009

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Re: CIE physics paper 2
« Reply #93 on: November 17, 2009, 01:52:58 am »
Amplitude can still be any displacement from an equilibrium position, and they had said that the first particle was displaced from the equilibrium by amplitude A and considering the second point is 180 degrees phase difference, it must have the same displacement as the first particle but in the opposite direction. The displacement has to -A because displacement is a vector quantity and so it has both magnitude and direction  ;).

Hey tyserius, i was wondering which variant paper you did?
« Last Edit: November 17, 2009, 02:15:53 am by kratos009 »
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Offline vince_24

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Re: CIE physics paper 2
« Reply #94 on: November 17, 2009, 02:42:42 am »
The phase difference was 270 degrees, was it not?
I am talking variant 2 here.
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Offline kratos009

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Re: CIE physics paper 2
« Reply #95 on: November 17, 2009, 03:41:43 am »
Yeah variant 2. I'm not exactly sure but i put 180 degrees, now that i think about it i think it is 270, cause the first particle is around 45 degrees from the start and the second particle is 45 degrees from the end. so together that's 90 degrees and 360-90= 270 degrees between them. But i'm pretty sure that the amplitude is -A because it has the same amplitude as the first particle but in a different direction, opposite direction so -A.
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Offline Tyserius

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Re: CIE physics paper 2
« Reply #96 on: November 17, 2009, 04:45:53 am »
Quote from: kratos009 on November 17, 2009, 03:41:43 am
Yeah variant 2. I'm not exactly sure but i put 180 degrees, now that i think about it i think it is 270, cause the first particle is around 45 degrees from the start and the second particle is 45 degrees from the end. so together that's 90 degrees and 360-90= 270 degrees between them. But i'm pretty sure that the amplitude is -A because it has the same amplitude as the first particle but in a different direction, opposite direction so -A.

Erm in a wave particles will still oscillate back up? So why negative A? The particles will still have maximum positive displacement so shouldn't the amplitude be A? And aren't they asking for the amplitude of the wave?
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Offline kratos009

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Re: CIE physics paper 2
« Reply #97 on: November 17, 2009, 05:05:51 am »
I remembered that in a past exam they had asked the amplitude on a part of the wave which was in the 'negative zone' and they had answered it as negative amplitude. I think the question was asking the displacement of that particle at that instant, and considering displacement is a vector quantity it was necessary to give the it as negative amplitude. I'm not 100% certain but i'm pretty sure that's what you have to do.

Plus I don't really want to think too much into the physics paper, what's done is done. I still got my Chemistry to go  :(. Lucky you tyserius you've finished :).
« Last Edit: November 17, 2009, 05:07:27 am by kratos009 »
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Offline Dooraven

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Re: CIE physics paper 2
« Reply #98 on: November 17, 2009, 07:40:32 am »
Quote from: vince_24 on November 17, 2009, 01:40:14 am
Amplitude is the maximum displacement. Antinode is place of maximum displacement. The point wasn't at an antinode so how exactly would the amplitude be A? Please enlighten me. Thanks.

The Question said the Amplitude of X is a A, not the maximum displacement. Y has the same magnitude of X but in a different direction so its A or -A. An amplitude is the maximum displacement of a particle in a wave, in a stationary wave the position of the particle does not change as it is not moving (hence stationary wave) therefore the displacement of the particle is the same as its amplitude.

The phase difference between the two points is 180 degrees. 270 would be correct if this was a progressive wave. However as this is a stationary wave the points can only vibrate with a 180 or 0 degrees phase difference because the phase difference between of any two points between any 2 nodes is zero. See here: http://www.btinternet.com/~melee3d/revision/physics/wavebehaviour.pdf under "Standing Waves"

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Offline MaNi_DaDuDe

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Re: CIE physics paper 2
« Reply #99 on: November 17, 2009, 10:31:29 am »
Quote from: Dooraven on November 17, 2009, 07:40:32 am
http://www.btinternet.com/~melee3d/revision/physics/wavebehaviour.pdf under "Standing Waves"



Nice link.

Wish I had seen that article before the exam. . . > . <
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Offline AndrewCedric

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Re: CIE physics paper 2
« Reply #100 on: November 17, 2009, 11:01:17 am »
Hey .. So what's the answer for the Amplitude in terms of A thingy??(( or sumthin like that.. the part hich has sationary waves))

And so the phase difference is 180 degrees?? if it is.. YEAHHHHHH.. Cause 270 degrees would be too vague. They only say state and there
is only 1 mark.. so i thought its 180 degrees..ahahah
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Offline astarmathsandphysics

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Re: CIE physics paper 2
« Reply #101 on: November 17, 2009, 12:37:24 pm »
Wait
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Offline astarmathsandphysics

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Re: CIE physics paper 2
« Reply #102 on: November 17, 2009, 12:41:14 pm »
I didnt realise this was about the paper just sat
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Offline MaNi_DaDuDe

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Re: CIE physics paper 2
« Reply #103 on: November 17, 2009, 12:46:42 pm »
Quote from: astarmathsandphysics on November 17, 2009, 12:41:14 pm
I didnt realise this was about the paper just sat

What do you mean?
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Offline josephwhite

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Re: CIE physics paper 2
« Reply #104 on: November 17, 2009, 01:26:44 pm »
dang. lost all the points in waves. but confident with the rest, especially the ball-and-plate question :D
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