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Physical meaning of second-order differential?

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  • Physical meaning of second-order differential?

    Anyone wants to try answering that?

  • #2
    yeah ....second order differential (I assume you mean second derivative ) physically represents acceleration of change

    second order differential equation models the dynamics (i.e. the WAY it is changing, stability in respects to he eigenvalues in the homogeneous equation) of a physical system.
    Last edited by RevolutionThroughReason; 07-10-2012, 02:18 AM. Reason: added more explanation for educational value
    [QUOTE=Afghanistan2010;658085][B]He is no different [COLOR="Red"]than us[/COLOR][/B],[B]he[COLOR="Red"] blindly believes [/COLOR]in the words [COLOR="Red"]of other men[/COLOR][/B],:[/QUOTE]

    2010 Admitting he's a blind believer not in God, but what other men says.

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    • #3
      Like dx/dt is velocity v. . . First order rate of change of x which represents lets say displacement in physical sense

      Then dv/dt is acceleration a . . . The Second order or rate of change of v

      Each with respect to time.

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      • #4
        Toramana here is an answer in layman terms

        first order: measures rate of change
        second order: measures rate of (rate of change)

        e.g.,
        x^3 is an odd function
        d/dx (x^3) = 3x^2 will give you a parabola
        d/dx ( d/dx (x^3) ) = 6x will give you a straight line.

        But perhaps this much you already know. Question can be why do you need it? Where is it used? Being a computer science person, I will give you a CS example. You might be familiar with the laplace filters in image processing. You can use it for blurring an image. The way it works is by taking an input mask (which is a sum of a second derivative w.r.t x and a second derivative w.r.t y), and you multiply (correct word = convolve) this filter with the original image. Another example from the same area is edge detection. What is an edge? Don't you think it is the rate of change between two points in an image? If you apply a second derivative to this variation, just identify the zero-crossings and you have your edge :-)

        This is also a key component in vector calculus so many examples can be given from world of physics also.

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        • #5
          If you mean

          v = dx/dt
          a = dv/dt = d²x/dt²

          which means,if you derivate the speed,you get the acceleration and if you derviate twice the route you get the acceleration aswell.
          High achievement always takes place in the framework of high expectation.

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          • #6
            I think toramana knows the acceleration velocity concept fellas, he might after something else here.

            Not dabbling in hamiltonian mechanics are you toramana ? stay away from that stuff
            It's enough that I know, Our time had a home, In your heart..Was a place..But the glass always breaks..

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            • #7
              Originally posted by RevolutionThroughReason View Post
              yeah ....second order differential (I assume you mean second derivative ) physically represents acceleration of change
              Yes, agree with that definition (the most general) i.e., approximates change in "rate of change" ....(very crude eg) My salary was 100 dollars at the end of 2010---got 5 dollars raise in salary for 2011, 8 dollars raise for 2012, 7 dollars 2013,---


              -first deriv
              (avg) change in salary over 3 years ---((105-100)+(113-105)+(120-113))/3

              -second deriv
              (avg) change in salary-raise over 3 years---- ((8-5)+(7-8))/3
              Last edited by Toramana; 07-10-2012, 06:53 PM.

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              • #8
                Originally posted by Talal View Post
                I think toramana knows the acceleration velocity concept fellas, he might after something else here.

                Not dabbling in hamiltonian mechanics are you toramana ? stay away from that stuff
                Actually, am studying Riemannian geometry in the hope if I could apply it where I want to. But every math is fascinating---I am studying a book "The historical development of the calculus"---nice book describing as how various ideas in calculus originated.
                Last edited by Toramana; 07-10-2012, 09:40 PM.

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                • #9
                  Originally posted by Toramana View Post
                  Actually, am studying Riemannian geometry in the hope if I could apply it where I want to. But every math is fascinating---I am studying a book "The historical development of the calculus"---nice book describing as how various ideas in calculus originated.


                  really? ....My area of interest right now is Differential Geometry (which Riemannian Geometry is heavily influential as it introduced the concept of Manifolds).

                  Mainly my interest is to understand spatial curvature of objects over large distances. But I m also getting introduced to synthetic differential geometry now which deals primarily with the study of shape operators and curvature without a metric space. This is fascinating; it employs more Abstract Algebraic concepts of set relationships and topology than Riemannian stuff; sometimes it's hard to wrap my head around how exactly it can be "Differential" Geometry when we are not dealing with metric spaces.
                  [QUOTE=Afghanistan2010;658085][B]He is no different [COLOR="Red"]than us[/COLOR][/B],[B]he[COLOR="Red"] blindly believes [/COLOR]in the words [COLOR="Red"]of other men[/COLOR][/B],:[/QUOTE]

                  2010 Admitting he's a blind believer not in God, but what other men says.

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                  • #10
                    Originally posted by Afghanistan2010 View Post
                    If you mean

                    v = dx/dt
                    a = dv/dt = d²x/dt²

                    which means,if you derivate the speed,you get the acceleration and if you derviate twice the route you get the acceleration aswell.


                    and if you derivate twice the route? what are you saying? LOL
                    [QUOTE=Afghanistan2010;658085][B]He is no different [COLOR="Red"]than us[/COLOR][/B],[B]he[COLOR="Red"] blindly believes [/COLOR]in the words [COLOR="Red"]of other men[/COLOR][/B],:[/QUOTE]

                    2010 Admitting he's a blind believer not in God, but what other men says.

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                    • #11
                      Originally posted by RevolutionThroughReason View Post
                      really? ....My area of interest right now is Differential Geometry (which Riemannian Geometry is heavily influential as it introduced the concept of Manifolds).

                      Mainly my interest is to understand spatial curvature of objects over large distances. But I m also getting introduced to synthetic differential geometry now which deals primarily with the study of shape operators and curvature without a metric space. This is fascinating; it employs more Abstract Algebraic concepts of set relationships and topology than Riemannian stuff; sometimes it's hard to wrap my head around how exactly it can be "Differential" Geometry when we are not dealing with metric spaces.
                      Thanks for the clue. I want to study RG and related topics as deeply as time allows me. Could you recommend a good book on differential geometry and differential synthetic geometry? Shape operators etc. are the things I am interested in.

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                      • #12
                        Originally posted by Toramana View Post
                        Thanks for the clue. I want to study RG and related topics as deeply as time allows me. Could you recommend a good book on differential geometry and differential synthetic geometry? Shape operators etc. are the things I am interested in.


                        well honestly; for synthetic differential geometry; I highly recommend you tackle fundamentals of theoretical mathematics first like Abstract Algebra , topology Algebraic Topology first or it will seem like an alien language; in fact it almost is.

                        Well I'm not sure which level of differential geometry you are but these are the books I started with for Classical Differential Geometry



                        Elementary Differential Geometry by Pressley
                        Elementary Differential Geometry by O'Neill
                        Lectures on Classical Differential Geometry by Struik
                        all these are amazing

                        now for more advanced stuff which emphasizes Riemannian Geometries and Manifolds

                        Differential Geometry of Curves and Spaces by DoCormo this is THE BEST book but it is advanced, Try one of the earlier books first
                        Comprehension Introduction to Differential Geometry by Spivak is amazing, but it's extremely rigorous; and there are volumes; I don't own it, but I have seen it it is very expensive.
                        Differential Geometry - Curves-Spaces-Manifolds by Kuhnel, I used this one for my course, it's ok but I like DoCormo better.

                        for Synthetic Differential Geometry; I don't have any specific book; just various pamplets people who are experts in that field send to me.
                        [QUOTE=Afghanistan2010;658085][B]He is no different [COLOR="Red"]than us[/COLOR][/B],[B]he[COLOR="Red"] blindly believes [/COLOR]in the words [COLOR="Red"]of other men[/COLOR][/B],:[/QUOTE]

                        2010 Admitting he's a blind believer not in God, but what other men says.

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                        • #13
                          Originally posted by RevolutionThroughReason View Post
                          well honestly; for synthetic differential geometry; I highly recommend you tackle fundamentals of theoretical mathematics first like Abstract Algebra , topology Algebraic Topology first or it will seem like an alien language; in fact it almost is.

                          Well I'm not sure which level of differential geometry you are but these are the books I started with for Classical Differential Geometry



                          Elementary Differential Geometry by Pressley
                          Elementary Differential Geometry by O'Neill
                          Lectures on Classical Differential Geometry by Struik
                          all these are amazing

                          now for more advanced stuff which emphasizes Riemannian Geometries and Manifolds

                          Differential Geometry of Curves and Spaces by DoCormo this is THE BEST book but it is advanced, Try one of the earlier books first
                          Comprehension Introduction to Differential Geometry by Spivak is amazing, but it's extremely rigorous; and there are volumes; I don't own it, but I have seen it it is very expensive.
                          Differential Geometry - Curves-Spaces-Manifolds by Kuhnel, I used this one for my course, it's ok but I like DoCormo better.

                          for Synthetic Differential Geometry; I don't have any specific book; just various pamplets people who are experts in that field send to me.
                          Thanks Bacha. Nice of you.
                          Last edited by Toramana; 07-11-2012, 06:40 PM.

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                          • #14
                            Originally posted by RevolutionThroughReason View Post
                            well honestly; for synthetic differential geometry; I highly recommend you tackle fundamentals of theoretical mathematics first like Abstract Algebra , topology Algebraic Topology first or it will seem like an alien language; in fact it almost is.

                            Well I'm not sure which level of differential geometry you are but these are the books I started with for Classical Differential Geometry



                            Elementary Differential Geometry by Pressley
                            Elementary Differential Geometry by O'Neill
                            Lectures on Classical Differential Geometry by Struik
                            all these are amazing

                            now for more advanced stuff which emphasizes Riemannian Geometries and Manifolds

                            Differential Geometry of Curves and Spaces by DoCormo this is THE BEST book but it is advanced, Try one of the earlier books first
                            Comprehension Introduction to Differential Geometry by Spivak is amazing, but it's extremely rigorous; and there are volumes; I don't own it, but I have seen it it is very expensive.
                            Differential Geometry - Curves-Spaces-Manifolds by Kuhnel, I used this one for my course, it's ok but I like DoCormo better.

                            for Synthetic Differential Geometry; I don't have any specific book; just various pamplets people who are experts in that field send to me.
                            Those are some solid books. You seem like you know your stuff.
                            Even Adobe Photoshop can't change me.

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                            • #15
                              Originally posted by Admin Khan View Post
                              Those are some solid books. You seem like you know your stuff.
                              truthfully I have barely touched the tip of the ice berg .....when I first started I wasn't even interested, but then I met a guy and asked him what he was doing his research on and I got swayed into it.
                              [QUOTE=Afghanistan2010;658085][B]He is no different [COLOR="Red"]than us[/COLOR][/B],[B]he[COLOR="Red"] blindly believes [/COLOR]in the words [COLOR="Red"]of other men[/COLOR][/B],:[/QUOTE]

                              2010 Admitting he's a blind believer not in God, but what other men says.

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