Physics: transverse wave & wavelength & motion

  • Thread starter YMMMA
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  • #1
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Homework Statement


the question asks at which point is the string moving upward at the instant shown?

Homework Equations


No equations needed

The Attempt at a Solution



I am not sure how I should approach this type of questions.
A) will move downward
B) downward then upward
C) upward then downward
D) same as C
E)upward then downward
Am I correct?
 

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Answers and Replies

  • #3
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The upward direction is the direction of the y ^ arrow , -if you simply start at the left 0 and follow
the string with a pen top you will find there are TWO of the points from the A-B-C-D-E list of shown points
where where your pen top is travelling upward in the general direction of y ^.
 
  • #4
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The upward direction is the direction of the y ^ arrow , -if you simply start at the left 0 and follow
the string with a pen top you will find there are TWO of the points from the A-B-C-D-E list of shown points
where where your pen top is travelling upward in the general direction of y ^.
So, you’re saying it could be C and E,right?
I understand now that pointing away from the x axis means upward and pointing toward the x axis means downward,yes?
 
  • #5
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y^ is upward above 0 , y ∨ [downward arrow] below 0 is , of course, downward. By convention (Cartesian axes) y^ is usually
only given.
For representing waveforms / "string" , negative numbers of y ( ∨ or y below 0 ) are not that important -for SATS anyway-
The amplitude of the waveform ,or maximum distance from the horizontal x axis, can be taken at the turning point ("crest")
above the x axis , namely point A. [ since below is a mirror image in the question]
Sorry, my bad, I overlooked D aswell. Your pen top will be travelling upward [ direction y^] at that point as well.
Please give the actual question at the start.
 
  • #6
156
10
y^ is upward above 0 , y ∨ [downward arrow] below 0 is , of course, downward. By convention (Cartesian axes) y^ is usually
only given.
For representing waveforms / "string" , negative numbers of y ( ∨ or y below 0 ) are not that important -for SATS anyway-
The amplitude of the waveform ,or maximum distance from the horizontal x axis, can be taken at the turning point ("crest")
above the x axis , namely point A. [ since below is a mirror image in the question]
Sorry, my bad, I overlooked D aswell. Your pen top will be travelling upward [ direction y^] at that point as well.
Please give the actual question at the start.
Here is it in full. I actually solved it as D before posting this. Can we say that points C and E are the nodes so at this instant they’re neither up or down?
 

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  • #7
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Here I think its clear that spoke P will move up, but Q will move up then down. Answer is A so Q will move down. Should I approach the question above the same as this one?
Here’s an explanation for this one. But still I am confused.
 

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  • #8
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Q6 one wavelength = two 'loops' . Answer?
 
  • #9
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Q6 one wavelength = two 'loops' . Answer?
Answer C
 
  • #10
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Correct. Question 7 isn't in the English language.
Q 8 Hint Forget about nodes. D is correct, but is your pen top going upward at any any other points aswell?
 
  • #11
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Correct. Question 7 isn't in the English language.
Q 8 Hint Forget about nodes. D is correct, but is your pen top going upward at any any other points aswell?
7 asks about twice the period, so E

Pen top points upward at 3 points as you said earlier..

What confuses me more is the other question, should approach post #1 the same way?
 
  • #12
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No, I think the graph (Side View) shows the x axis as velocity.. There is no origin 0 given and the other axis (y axis ) is
displacement. This is a travelling wave, so as the answer says- the next point p towards the origin 0 at extreme left,i.e the preceding dot
is
for point P - HIGHER than point P ∴ P will move upwards
for point Q - LOWER than point Q ∴ Q will move downwards

You could label the preceding ' dots' for P as Po
.........................................................for Q as Qo ____ so P is P1 and Q is Q1
 
  • #13
156
10
No, I think the graph (Side View) shows the x axis as velocity.. There is no origin 0 given and the other axis (y axis ) is
displacement. This is a travelling wave, so as the answer says- the next point p towards the origin 0 at extreme left,i.e the preceding dot
is
for point P - HIGHER than point P ∴ P will move upwards
for point Q - LOWER than point Q ∴ Q will move downwards

You could label the preceding ' dots' for P as Po
.........................................................for Q as Qo ____ so P is P1 and Q is Q1
Got it, thanks!
But this question is different from the other?
 
  • #14
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If it’s the same question would be followed reasoning be correct? >>> Like point Aο lower that A so downward, same goes with all. Except in B will move upward?
 
  • #15
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Ahh... I took your first post #1 too literally . The x-axis here is distance (horizontal). The question would / should have said
when is the transverse wave/string moving upward . Since its motion is perpendicular to the x-axis, the only possible answer
is A.
In the second part /second question - which you understand - the x-axis is velocity , so your reasoning in #14 would be incorrect.
 
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  • #16
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Ahh... I took your first post #1 too literally . The x-axis here is distance (horizontal). The question would / should have said
when is the transverse wave/string moving upward . Since its motion is perpendicular to the x-axis, the only possible answer
is A.
In the second part /second question - which you understand - the x-axis is velocity , so your reasoning in #14 would be incorrect.
Understood, Thank you!
 

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