Wikipedia:Reference desk/Archives/Science/2015 March 13

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March 13

The coordinates of the physical body in space

Is it possible to determine the coordinates of the physical body in space, knowing only one unit of the dynamics of energy of this physical body, such as for example the impulse or speed (acceleration), or gravity?--83.237.204.197 (talk) 10:07, 13 March 2015 (UTC)

I am not sure that I understand the question, but I think that the answer is no. The coordinates of a physical object in space include three position coordinates (x, y, and z, unless those are transformed to another coordinate system such as geocentric or heliocentric, which is still three coordinates) and three velocity or momentum coordinates, which is six coordinates, as well as mass. If I understand the question, you can't get that much information from one scalar or one vector. The question is very vague, but seems to have enough information to give an answer of no to whatever it is asking for. Robert McClenon (talk) 14:08, 13 March 2015 (UTC)

Thanks a lot. I’m supposed that it is been possible to solving a mathematical equation or (combined) system of mathematical equations with much more mathematical variables which could not be known.--83.237.192.70 (talk) 14:45, 13 March 2015 (UTC)

No matter what, you need a minimum of 6 numbers (three translation and three rotation) - it doesn't matter whether you choose polar, cylindrical or some other projection for the position or a matrix or quaternion for rotation, the answer is the same. Even if you have an initial position from some time in the past and acceleration/velocity/time and use that to calculate the present position - you can't escape the need for those 6 numbers. It's a fundamental property of geometry in three dimensions.

That said, you might possibly be able to constrain the problem by (in effect) forcing some of those numbers to always be the same and then omitting them...so, for example, if you define the "initial position" to be the origin of your coordinate system and specify that the 'thrust' of some motor is applied down the X axis of the body - then you need fewer actual numbers because you've effectively forced the remainder to be zeroes.

You might imagine something like defining the position of a railroad locomotive as the distance from one city to the next - now you only need that one coordinate to specify the full position and rotation of the locomotive - but you're still implying more numbers in the description of the path of the track and that the position of the locomotive relative to it is always zero. SteveBaker (talk) 15:16, 13 March 2015 (UTC)

Just to add a bit to SteveBaker's excellent answer, the three translation dimensions are commonly known by their Cartesian coordinate names of "X", "Y", and "Z", or think of them as "up-down", "left-right" and "forward-back"; or perhaps "height", "depth", and "width". Most people have an intuitive sense of those. The three rotational dimensions are familiar to pilots, who are used to dealing with them where they are called "pitch", "yaw", and "roll", which represent rotations around each of the three Cartesian axes (in the case of flight dynamics, roll is rotation around the axis you are traveling in, yaw is rotation around the vertical axis and pitch is rotation around the perpendicular horizontal axis). You can read more about these things at Degrees of freedom (mechanics), which discusses all six. --Jayron32 15:25, 13 March 2015 (UTC)

It is only the position vector that locates points in 3D space and it has simply three spacial coordinates with respect to a reference origin. Linear and rotational speed, velocity, instantaneous velocity and acceleration are all derivatives and functions of position with respect to time, but these do not indicate or specify where any bodies or particles happen to be (such as in my backyard or on Mars). Knowing their energy does not tell you where either. Also, knowing their orientation or angular position does not tell you where. With spacetime things get more complicated, but that is because one is including when as well as where something happens to be within a relativistic framework. -Modocc (talk) 15:56, 13 March 2015 (UTC)

Dynamics of physical processes - the dynamics of algebraic numbers (multipliers) is always told that as the more coordinates in space had a physical body, so the easier it is to find all of these coordinates.--83.237.207.145 (talk) 16:09, 13 March 2015 (UTC)

I'm not sure, but you might be getting confused with Overdetermined_systems and Underdetermined_systems - these are concepts from pure math, but they come in to dynamical systems and our models of physical processes. SemanticMantis (talk) 18:02, 13 March 2015 (UTC)

At in the end, it is always get's the momentum change of impulse of the physical body, and we always know what is it the momentum change of impulse during in time.--83.237.203.10 (talk) 06:55, 14 March 2015 (UTC)

Momentum changes of impulse in the nature, it is a coordinates in space, hence ∆p = x, y, z, . . .--85.141.235.173 (talk) 07:47, 14 March 2015 (UTC)

Possible quantity of multipliers in the calculations of the computer is been unlimited, so that the quantity of mathematical variables or mathematical functions for the computer did not had been matter, if a logic of computer program been could.--83.237.199.114 (talk) 15:56, 14 March 2015 (UTC)

help identify

what type of insulation is this? White glass wool / mineral wool?

http://3.ii.gl/91CapTPCG.jpg — Preceding unsigned comment added by 86.102.0.109 (talk) 14:41, 13 March 2015 (UTC)

Hard to say from the picture alone. It could be Glass wool (sometimes called fiberglass in the U.S.), Mineral wool, or even Asbestos. They all can look like the picture you've shown. --Jayron32 15:05, 13 March 2015 (UTC)

For my tuppence worth is is POLYFIL. It is white. Glass fiber ranges from yellow to pink. Also, glass fiber makes employees assembling speaker cabinets itch and thus make polyfil a better option. The other thing is that the image shows and Italian speaker and their stuff cheap and nasty *@ #מ₪!.--Aspro (talk) 15:30, 13 March 2015 (UTC)

• This is speaker sound-deadening material, probably as Aspro said, POLYFIL, a plastic polymerRead-write-services (talk) 04:04, 16 March 2015 (UTC)

Where do Lithium-ion batteries go, when they die?

According to Lithium-ion_battery#Environmental_concerns_and_recycling, it's cheaper to mine new minerals than to recycle. I wonder however, why is it like that? Finding ores, extracting the lithium, cobalt and other minerals, transporting it... What makes the recycling to expensive? After all, you already have the minerals encased at the right amounts at hand, if you collect the batteries. --Fend 83 (talk) 22:22, 13 March 2015 (UTC)--Fend 83 (talk) 22:22, 13 March 2015 (UTC)

If you read this it is not economical presently due to the small amount of lithium carbonate in the batteries but recycling is expected to become more viable (and indeed necessary) in the future "to hedge against the uncertain and potential price fluctuations arising due to geo-political or other barriers". Richerman (talk) 18:44, 14 March 2015 (UTC)