Qualification > Sciences
CIE physics paper 2
kratos009:
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.
Tyserius:
--- 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.
--- End quote ---
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?
kratos009:
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 :).
Dooraven:
--- 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.
--- End quote ---
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"
MaNi_DaDuDe:
--- Quote from: Dooraven on November 17, 2009, 07:40:32 am --- http://www.btinternet.com/~melee3d/revision/physics/wavebehaviour.pdf under "Standing Waves"
--- End quote ---
Nice link.
Wish I had seen that article before the exam. . . > . <
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