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Physics: Post your doubts here!

angelicsuccubus

angelicsuccubus

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Jaf said:
Uh... no. That not how it will be.
1) It lags. That means any particular crest/trough will appear later in time. In your drawing, it appears earlier. Had it been a displacement-distance graph, the sketch would have been correct (almost (see below) ... :p )
2) Both, can't obviously start from A.

Here's a picture of my drawing:
View attachment 11098
Click to expand...
Jaf you're right about it not starting from the same point but otherise I don't agree with you... can you prove it somehow? I mean I get what you're saying that if it lags, it's slower and it should appear later.. but the wording of the question "lags behind T1 by a phase angle of 60 degrees" is concordent with my drawing.

Edit: you know what now Im just confused.. you might be right but I can't make up my mind.. need more opinions
 
angelicsuccubus

angelicsuccubus

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abcde said:
AoA! angelicsuccubus: I think you sort of misread the question. The answer requires a sketch of the same stationary wave 0.25 T later. There's no change in period. So the correct sketch would simply be a straight horizontal line (on the dotted line). leosco1995: In case you're confused, check this simulation: http://en.wikipedia.org/wiki/File:Standing_wave.gif :)
At t = 0s, the graph is as shown in the question
At t= 0.25 T, the graph is a straight horizontal line
At t= 0.5 T, the graph is again sinusoidal with the antinode 'crest' now being the 'trough' while the nodes remain exactly the same.
At t = 0.75 T, the graph is again a straight horizontal line
At t = T, the same graph as the question again.
(This only applies to a stationary wave. A progressive wave sketch is never horizontal at any time.)
Click to expand...
shoot me.. I should go sleep so I wouldnt do this in the exam.. sorry leosco1995
 
angelicsuccubus

angelicsuccubus

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Saad (سعد) said:
Okay...

In the syllabus, we have:

(e) describe the effect of a uniform electric field on the motion of charged particles.

And in the notes, I have things like Equipotential Surface, Potential Gradient, and 'Electric field lines must meet the surface at right angles'.

... What in the realm of Physics is this?
Click to expand...
lol that's A2 stuff you mentioned..
 
G

geek101

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Question about the impulse....if there are two objects with the same mass and volume and moving with the same speed, one is hard and one is soft...what is the difference between the impulse of each?
 
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Famous4it

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Hi I have a few questions if someone could help me out, that would be great:
Can someone help me out with diffraction grating? That formula where you figure out the number of fringes.
2. how does the colour of the light and width of the slits affect the fringes (brightness, spacing)
3. And I read something about how when the slits are wider, intensity is less and so the fringes are darker. Is that right?
 
angelicsuccubus

angelicsuccubus

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K

knight101

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t= 0.35 +/- 0.01

can anyone tell me how to calculate the uncertainty in t^2 ? last time I did this I was in AS so i forgot :/
 
Jaf

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raamish said:
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s10_qp_21.pdf

5c) The arrow will be pointed up and down in a somewat curved direc. yes?
Why are we resolving the distance. why cant we take out the answer without resoolving the distance?
Click to expand...
No, of course not.
There's a couple being created; how in the world will the arrows be curved?

Both arrows are parallel to the direction of the field. The arrow from P point in the direction of the field. The arrow from N points in the opposite direction. The reason is that the right end is negative (hence the direction of the field from left to right) and the unlike charges attract.
I asked my teacher today if the particles will continue to move until they line up along the direction of the field and she said no because we don't know if there's a large enough force being created by the electric field to achieve sufficient rotation.

We don't necessarily have to resolve the distance. The force can be resolved too and you'll get the same answer.
angelicsuccubus said:
Jaf http://www.thestudentroom.co.uk/showthread.php?t=430543 ... so do we draw it after T1 or before?
Click to expand...

After. It's kind of hard to explain why. :S
 
angelicsuccubus

angelicsuccubus

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Jaf said:
No, of course not.
There's a couple being created; how in the world will the arrows be curved?

Both arrows are parallel to the direction of the field. The arrow from P point in the direction of the field. The arrow from N points in the opposite direction. The reason is that the right end is negative (hence the direction of the field from left to right) and the unlike charges attract.
I asked my teacher today if the particles will continue to move until they line up along the direction of the field and she said no because we don't know if there's a large enough force being created by the electric field to achieve sufficient rotation.

We don't necessarily have to resolve the distance. The force can be resolved too and you'll get the same answer.

After. It's kind of hard to explain why. :S
Click to expand...
That's what I thought about the forces on P and N exactly but wasn't gonna risk it..

And I do get what you're saying about the lag thing.. but these people are debating over it.. and the "model answer" booklet I have for these past papers.. has it drawn before T1..
 
R

raamish

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Jaf said:
No, of course not.
There's a couple being created; how in the world will the arrows be curved?

Both arrows are parallel to the direction of the field. The arrow from P point in the direction of the field. The arrow from N points in the opposite direction. The reason is that the right end is negative (hence the direction of the field from left to right) and the unlike charges attract.
I asked my teacher today if the particles will continue to move until they line up along the direction of the field and she said no because we don't know if there's a large enough force being created by the electric field to achieve sufficient rotation.

We don't necessarily have to resolve the distance. The force can be resolved too and you'll get the same answer.

After. It's kind of hard to explain why. :S
Click to expand...
So in couple the arrows will always be parrallel u say?The arrows will be left and right or up and down.And why didnnt we take cos to resolve.
 
Jaf

Jaf

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raamish said:
So in couple the arrows will always be parrallel u say?The arrows will be left and right or up and down.And why didnnt we take cos to resolve.
Click to expand...
Yeah.

Because then it'd be wrong. I can't explain trigonometry here.
 
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