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Science GIFS

Dave

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Re: Science GIFS
« Reply #120 on: July 11, 2017, 04:27:36 PM »
:watching: Yes....

Yes... that is a good one too.

I also like this one.


So do I, so long as it stays on your side of the Pond!

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Essie Mae

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Re: Science GIFS
« Reply #121 on: July 12, 2017, 08:23:11 PM »
I particularly like the sine wave and the herd immunity but they are all brilliant.
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Essie Mae

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Re: Science GIFS
« Reply #122 on: July 12, 2017, 08:38:26 PM »
Incidentally, what are the applications of sine waves?
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Dave

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Re: Science GIFS
« Reply #123 on: July 12, 2017, 09:29:56 PM »
Incidentally, what are the applications of sine waves?

Can't remember that gif, was it something like a spoke or radius rotating in a circle with the resultant wave form?

In both mechanical and electrical theory sine waves are very important, they are the "shape" of the electricity from your sockets, the basic shape of the "carrier signal" in radio transmissions and the shape of any pure audio tone. It is also the wave shape that would be drawn by a weight bouncing up and down on a spring. Remember the old "Spirograph"? That could draw sine waves if you set it up right, even sine waves in a circle to make sort of flower patterns - great fun!

The number of waves per second gives you the frequency, so a 1 kiloHertz tone would be 1000 full waves, or cycles,, like a "S" on its side, per second. Hertz was the guy credited with discovering this cyclic nature when he nannaged to transmit energy, through the air,  from a "transmitter" to a "receiver" - Marconi cashed in by sending "intelligence", a Morse code message, using Hertz' principles.



Wikipedia has, of course, an article on them: https://en.m.wikipedia.org/wiki/Sine_wave. The full name is "sinusoidal waveform"
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Icarus

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Re: Science GIFS
« Reply #124 on: July 12, 2017, 09:58:05 PM »
Another curiosity: Imagine that you have attached a tiny light to the bottom sidewall of an auto tire. When the automobile moves, the light will describe a half sine wave. 

hermes2015

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Re: Science GIFS
« Reply #125 on: July 13, 2017, 07:36:59 AM »
Another curiosity: Imagine that you have attached a tiny light to the bottom sidewall of an auto tire. When the automobile moves, the light will describe a half sine wave.

I may be wrong, but I thought the light would describe a cycloid curve?
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Essie Mae

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Re: Science GIFS
« Reply #126 on: July 13, 2017, 08:47:16 PM »
Thanks for that Gloucs, Icarus and Hermes. I don't pretend to fully understand your replies but I sort of get it and I do remember being quite fascinated by the Spirograph. I am not a trained maths teacher, but when I was doing Home Hospital teaching, there were no GCSE maths teachers so I had to do it and thoroughly enjoyed it and managed to get by with lots of preparation but didn't always know why I was teaching it.
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Dave

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Re: Science GIFS
« Reply #127 on: July 13, 2017, 09:46:44 PM »
Another curiosity: Imagine that you have attached a tiny light to the bottom sidewall of an auto tire. When the automobile moves, the light will describe a half sine wave.

I may be wrong, but I thought the light would describe a cycloid curve?

Hmm, if you think of it a pen in a rotating disc with a sheet of paper sliding past under it - so the pen draws the sine wave on the paper - seems no different than the paper being still and the disc rolling along. The latter being analogous to the light/wheel set-up.

But you have me wondering now!

OK, checked on it, you are correct, Hermes, the rolling wheel gives a cycloid.

Something to think about there!
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Icarus

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Re: Science GIFS
« Reply #128 on: July 14, 2017, 12:54:04 AM »
You two are both correct. The path of the light is in fact cycloidal. Shame on me for claiming otherwise. .... I had to lay it out on a sheet of paper to prove it to myself. That is a quirk of mine....the do it yourself thing.... it would be much easier to consult Wikipedia, which I did after the fact. Sure enough a good explanation is there on Wiki.  Better mental exercise to do it on a sheet of paper with the trusty calculator close at hand.  The presence of the calculator implies that there is a limit to ones dedication to mental exercise.  :cauldron:

OK how 'bout we toss a rock toward the nasty neighbors window, and trace its path? Sinusoidal?  That does have the critical exponent two in the equation.

hermes2015

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Re: Science GIFS
« Reply #129 on: July 14, 2017, 05:26:27 AM »
OK how 'bout we toss a rock toward the nasty neighbors window, and trace its path? Sinusoidal? ....

No, ideally parabolic, but a bit distorted owing to atmospheric drag.
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hermes2015

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Re: Science GIFS
« Reply #130 on: July 14, 2017, 05:53:44 AM »
To take the wheel and light setup further, if one did not place the light on the rim, but somewhere else on the wheel, would its path still be a cycloid?

Dead centre, on the axle, the path would be a straight line, but what about, say, halfway along the radius? Or even at a point beyond the rim (greater than the radius)?
« Last Edit: July 14, 2017, 06:40:26 AM by hermes2015 »
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Arturo

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Re: Science GIFS
« Reply #131 on: July 14, 2017, 07:15:03 AM »
To take the wheel and light setup further, if one did not place the light on the rim, but somewhere else on the wheel, would its path still be a cycloid?

Dead centre, on the axle, the path would be a straight line, but what about, say, halfway along the radius? Or even at a point beyond the rim (greater than the radius)?

What if you put the light on the tread facing outwards, and say the wheel is alone, rotating as it normally would, in space?

EDIT: Like this
Spoiler: ShowHide

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Dave

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Re: Science GIFS
« Reply #132 on: July 14, 2017, 07:37:15 AM »
To take the wheel and light setup further, if one did not place the light on the rim, but somewhere else on the wheel, would its path still be a cycloid?

Dead centre, on the axle, the path would be a straight line, but what about, say, halfway along the radius? Or even at a point beyond the rim (greater than the radius)?

We need a Spirograph to play with!

@ Icarus: "I need to see for myself", or, "I need to work it out for myself" has always been my problem in fully understanding, or perhaps accepting, things as well. It is not "real" unless I can see it physically demonstrated in some cases. There are, of course, things one just has to accept - building a nuclear reactor at home is hardly practical . . .
« Last Edit: July 14, 2017, 07:52:45 AM by Gloucester »
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Magdalena

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Re: Science GIFS
« Reply #133 on: July 14, 2017, 07:38:59 AM »
^^^
Sorry, I don't know what you guys are talking about.
I'm just gonna post a GIF...that's all.
****************

:watching: Yes....

Yes... that is a good one too.

I also like this one.




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Dave

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Re: Science GIFS
« Reply #134 on: July 14, 2017, 08:21:24 AM »
To take the wheel and light setup further, if one did not place the light on the rim, but somewhere else on the wheel, would its path still be a cycloid?

Dead centre, on the axle, the path would be a straight line, but what about, say, halfway along the radius? Or even at a point beyond the rim (greater than the radius)?

What if you put the light on the tread facing outwards, and say the wheel is alone, rotating as it normally would, in space?

EDIT: Like this
Spoiler: ShowHide


Not sure if being on the edge or half way across the tread makes much difference.

In terms of the sine wave or whatever being described a sort of "relativity" must come into place - the relsaive motions of the object (the wheel) and whatever is being "written" on. It is the conversion from rotational to linear motion, the relative position of a point on each component over time . . . sort of.

As for the space station: what is its "partner" in the "relativity" dance? Where are you, the observer, standing? This is a case of frequency of rotation versus the velocity of overall motion against the background. The rotational frequency of the car wheel is directionally proportional to its velocity on the road (assuming no wheel spins or skids!)- or its passing the stationary observer. The space station has no real constraints in the difference between its rotational frequency and linear velocity through free space. Thus a point on its edge could describe any possible shape, cycloid, a series of loops etc.

So, new question, what wave shapes are produced if the velocity if the linear motion of the rotating station through space is less or greater than its "equivalent" velocity if it was rolling along a surface?
« Last Edit: July 14, 2017, 08:50:42 AM by Gloucester »
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