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  • Acceleration is

    The rate of change of Veolcity
    Byron Boucher
    Burnet, TX

  • #2
    Or the second derivative of position with respect to time.

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    • #3
      bloody frightening!
      mark

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      • #4
        or force over mass. (freebody)

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        • #5
          Get going!!

          Thanks for that Byron.

          I suspect that this may have been prompted by that "other" "acceleration" thread.

          Now for a bit of "light reading" - and to set the fox and hounds off and running (and "yapping"?):

          Velocity:
          http://en.wikipedia.org/wiki/Velocity

          Acceleration:
          http://en.wikipedia.org/wiki/Acceleration

          Both velocity and acceleration - as vectors (they have magnitude and direction) - can be either positive (+ve) or negative (-ve).

          -ve acceleration is deceleration.

          A +ve change to +ve velocity = +ve acceleration.

          A -ve change to +ve velocity = -ve acceleration.

          A +ve change to -ve velocity = -ve acceleration.

          A -ve change to -ve velocity = +ve acceleration.

          etc.

          Oscar Wilde, in his 1893 play A Woman of No Importance, once famously referred to "the English country gentleman galloping after a fox" as "the unspeakable in full pursuit of the uneatable."
          from:
          http://en.wikipedia.org/wiki/Fox_hunting

          "Yoiks", "Yoiks" and "Tally-ho" and all that stuff!!!

          Comment


          • #6
            Originally posted by oldtiffie

            -ve acceleration is deceleration.
            Unless you learned mechanics from Lyndon Baines Johnson,
            then it would be deacceleration.

            :-) That is the obvious extrapolation of " De-escalation" .
            Surely I'm not the only one that was bothered by that. :-)
            ...lew...

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            • #7
              Deceleration

              Lew.

              Try this:
              http://en.wikipedia.org/w/index.php?...eration.&go=Go

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              • #8
                Definition?

                Acceleration is a sudden jerk on the handle when you are standing in a wagon.
                Bill

                Being ROAD KILL on the Information Super Highway and Electronically Challenged really SUCKS!!

                Every problem can be solved through the proper application of explosives, duct tape, teflon, WD-40, or any combo of the aforementioned items.

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                • #9
                  Originally posted by Lew Hartswick
                  Unless you learned mechanics from Lyndon Baines Johnson, then it would be deacceleration.
                  From a local TV weather reporter - "Tomorrow, clouds will be de-increasing."
                  Bill

                  Being ROAD KILL on the Information Super Highway and Electronically Challenged really SUCKS!!

                  Every problem can be solved through the proper application of explosives, duct tape, teflon, WD-40, or any combo of the aforementioned items.

                  Comment


                  • #10
                    Originally posted by bob_s
                    Or the second derivative of position with respect to time.
                    For machine tools, at least 4 are relevant to machine tool control systems:

                    Position
                    1st derivitive of position: speed/velocity
                    2nd derivative of position: acceleration
                    3rd derivative of position: rate of change of acceleration

                    The reason for concern with the third is that if you use constant acceleration (trapezoidal velocity profile), you jerk the machine tool around. You go from not applying force to the axis to suddenly applying a force and then suddenly removing it. An S curve velocity profile instead of a linear slope helps smooth this out. Technically, there is a 4th derivative and maybe more because you will be changing the 3rd.

                    http://zone.ni.com/devzone/cda/tut/p/id/4824
                    http://irtfweb.ifa.hawaii.edu/~tcs3/...311/scurve.PDF

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                    • #11
                      Originally posted by oldtiffie
                      Both velocity and acceleration - as vectors (they have magnitude and direction) - can be either positive (+ve) or negative (-ve).
                      What? Why would you bother with a vector with a negative magnitude? It's just a vector in the other direction. In fact, it's been a while since I studied it, but I thought vectors by definition have positive magnitudes.

                      (Edit: looking back at it, I'm guessing you were speaking of purely linear motion, and the + and - were the direction component of the vector. Carry on, I'll shut up now. Shoulda read more carefully )

                      -Pete
                      Last edited by Pete F; 12-03-2009, 08:58 PM.
                      I just like to make stuff.

                      Comment


                      • #12
                        H-d?

                        Don't worry about it Pete.

                        My main concern is controlling the third order derivative of my velocipede (OZ version of H-D?).

                        This is me in the pics in this link:
                        http://en.wikipedia.org/wiki/Velocipede

                        And our "Newsletter":
                        http://en.wikipedia.org/wiki/Velocipede_Illustrated

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                        • #13
                          acceleration, long straight road + hyabusa = soiled underwear
                          mark

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                          • #14
                            Originally posted by whitis
                            For machine tools, at least 4 are relevant to machine tool control systems:[/url]

                            Hate to be a #3, but your second link doesn't work!

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                            • #15
                              The definition requires refining.

                              "The rate of change of Velocity relative to something else."

                              This brings up the question of what really constitutes acceleration. Is a hovering helicopter undergoing acceleration by equal and opposite force vectors? It isn't moving relative to the Earth.

                              Is an orbiting satellite undergoing acceleration? It's velocity relative to the surface below it is not changing. Only it's velocity vector changes. Does it's potential energy change? If it were being accelerated then there should be a conversion of potential energy to kinetic energy.
                              Free software for calculating bolt circles and similar: Click Here

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