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Snapshot & History Graphs

  • Thread starter bcjochim07
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  • #1
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Homework Statement


asnapshot.jpg figure is asnapshot.jpg
aasnapshot.jpg correct & incorrect graphs is aasnapshot.jpg

Draw the history graph D(x=0m, t) at x= 0m for the wave shown in the figure.

Homework Equations





The Attempt at a Solution



I'm not quite understanding the concept of snapshot and history graphs. I think for this one the problem is that is is moving left. The graph that I drew is the wrong one. Here was my reasoning: In the figure, the graph is moving left, so shouldn't the leftmost point on the wave hit the point first? If at t=2 s this leftmost point is 1m away from x=0, then it takes 1 sec for it to arrive, so at t=3. I don't think I am visualizing this at all correctly. Could someone please explain to me why the graph on the bottom is correct? Thanks!
 

Answers and Replies

  • #2
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Any thoughts would be greatly appreciated.
 
  • #3
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I am confused and this is really bothering me.
 
  • #4
Redbelly98
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The Attempt at a Solution



I'm not quite understanding the concept of snapshot and history graphs. I think for this one the problem is that is is moving left. The graph that I drew is the wrong one. Here was my reasoning: In the figure, the graph is moving left, so shouldn't the leftmost point on the wave hit the point first?
Yes.

If at t=2 s this leftmost point is 1m away from x=0, then it takes 1 sec for it to arrive, so at t=3.
Yes, nothing happens (at x=0 m) until t = 3 sec.

I don't think I am visualizing this at all correctly. Could someone please explain to me why the graph on the bottom is correct? Thanks!
It's not correct. At x = 0, D is 0 until t=3 sec. The graph labeled "wrong" looks like the right one to me.
 
  • #5
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Yeah, see I'm having problems because there are a couple problems like this in my textbook where my drawings are completely off from what the back of the book has, so I was worried that I was not understanding this at all.
 
  • #6
Redbelly98
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Wow. What's the name of this book, and the authors? Looks like you understand it better than they do!
 
  • #7
My answer is the same as the original poster's..please, what are we doing wrong?!!??!
 
  • #8
Redbelly98
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Welcome to Physics Forums :smile:

You and the OP did it right, the book has it wrong.

What is the name of this book and its author?
 
  • #9
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The book's called Physics for Scientists and Engineers: A Strategic Approach (2nd ed.), Vol 3, and the author is Randall D. Knight. I also got the same answer as the OP. So the book is wrong and the OP is right?
 
  • #10
Redbelly98
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Welcome to PF :smile:

The book's called Physics for Scientists and Engineers: A Strategic Approach (2nd ed.), Vol 3, and the author is Randall D. Knight. I also got the same answer as the OP. So the book is wrong and the OP is right?
You are correct.

And thank you for answering my question :biggrin:
 
  • #11
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No problem :smile: Thanks for the help (and the fast reply)!
 
  • #12
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I have the 6th edition of this book and the answer in the answer key is still wrong....
 

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