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A tedious debate just need some backup.

  1. Jan 7, 2013 #1
    Ok, I'm having a debate about a silly concept with waves, about time/distance/speed and the quantity of waves passing different points.
    2 people now fail to comprehend these basic principals of reality, and are driving me insane..


    I have a client for whom I'm designing waves in Maya, who claims to believe that further out at sea, 5 waves pass per minute, but towards the shore, 6 waves pass per minute, without any new waves forming between them, as a consistent cycle; the statistics of the waves being always based on fixed values at different distances from the shore e.g. at 0 metres, they will always be moving at 20km/h, and at 200 metres from shore, will always be moving at 15km/h (random numbers).


    He fails to comprehend the fact that there is a set number of waves..
    He thinks that speeding them up will make more waves per minute pass one point than the previous.
    He does not understand that the waves consistently accelerating based on their distance from the shore will increase the gap between them in conjunction with the increase in speed and negate the difference between the quantity of waves passing a set point.

    When trying to tell a friend about this, things got even worse.. not only does my friend believe this guy's theory can physically exist, but he also believes that the waves will increase in number in a distance e.g. 200 metres from shore there may be 5 waves in 50 metres, but at 0 metres from shore there can be 6 waves in 50 metres, without them changing speed, with them all consistently remaining at 15km/h




    He believes that due to the volume of the waves increasing that the distance between the waves decreases, without their speed changing at all.
    I've tried explaining that distance is a part of speed, that you cannot increase the number of waves over a certain distance over time in this scenario without decreasing their speed, causing the following waves to begin to catch up, therefore negating the distance.
    He believes that the centre-points of the waves are irrelevant, that their volume growing, decreasing the distances between the edges of the waves, somehow increases the number of waves between a set point, while making the waves' centre-points further apart, without any of them changing speed.. He believes this so strongly and keeps trying to explain it to me, as though he has something to explain.. it's quite frustrating.

    He simply says:
    "You'll have more waves over the same distance without any changes in speed, because they'd all be travelling at the same speed because you're increasing the volume of the wave."


    I know it seems hopeless, I've tried explaining to him that you cannot change the distance between anything without adjusting the speed, and that the centrepoint of the wave is the only relevant information in this scenario, that the volume is not a part of the equation of speed, that increasing the volume does not decrease their distance apart in a way that is anything to do with how many waves spam a specific distance or pass a fixed point per minute.

    He still thinks that the waves coming closer together by their outer edges coming closer due to the waves expanding without their speeds changing somehow puts more waves within a set distance, and that the centre-points of the waves are irrelevant to the equation because it being a fluid makes it somehow specially exempt from the laws of physics.



    Anyhow, the full purpose of this post, is to simply ask for you to back me up on the obvious reality of it here, for those people to see it and maybe get some insight from others, and to make my life a little easier.
    Problem is I have Aspergers, and no matter what I say in person, it's not enough. All I do is give out the facts, even stress them.. then I'm told I'm wrong and that's that. Could use some support.



    Cheers,
    Tony
     
  2. jcsd
  3. Jan 8, 2013 #2

    Simon Bridge

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    Welcome to PF;
    Being right is not the same as being convincing ...

    Have a look through:
    http://oceanworld.tamu.edu/resources/ocng_textbook/contents.html
    Chapter 16 talks about ocean waves... at sea the frequencies are 4-6 waves per minute.

    Assertions are - for the ocean:
    1. a wave train can move from a fast region to a slow region and change frequency ...
    2. a wave train can have two different frequencies at the same speed ...

    Usually we expect the frequency to stay the same - all other things remaining equal.
    However - ocean waves may not follow the simple math you get at High School - all other things may not be equal. Could there be another influence? - I'd check the basic underlying assertions that the frequency of waves arriving at the beach is, indeed, different from the frequency at sea.
     
  4. Jan 8, 2013 #3

    A.T.

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    Why is he so obsessed with the speed remaining constant? It does indeed decrease. See:

    http://en.wikipedia.org/wiki/Wave_shoaling
    220px-Propagation_du_tsunami_en_profondeur_variable.gif
     
  5. Jan 8, 2013 #4
    Basically, your friend is right only in stating that the number of waves per length increases, but the implication of that is that the speed is also reduced, so, in the end, his statement is not correct.
     
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