Snapshot & History Graphs

by bcjochim07
Tags: graphs, history, snapshot
 P: 374 1. The problem statement, all variables and given/known data figure is asnapshot.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. 2. Relevant equations 3. 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!
 P: 374 Any thoughts would be greatly appreciated.
 P: 374 I am confused and this is really bothering me.
Mentor
P: 12,071
Snapshot & History Graphs

 Quote by bcjochim07 3. 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.
 P: 374 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.
 Mentor P: 12,071 Wow. What's the name of this book, and the authors? Looks like you understand it better than they do!
 P: 1 My answer is the same as the original poster's..please, what are we doing wrong?!!??!
 Mentor P: 12,071 Welcome to Physics Forums You and the OP did it right, the book has it wrong. What is the name of this book and its author?
 P: 2 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?
Mentor
P: 12,071
Welcome to PF

 Quote by Klorey 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
 P: 2 No problem Thanks for the help (and the fast reply)!
 P: 70 I have the 6th edition of this book and the answer in the answer key is still wrong....

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