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Engineering LibreTexts

7.4.1: Energy in Linear Acceleration Coordinate

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  • The potential is defined as
    P.E. = - \int_{ref}^2 \pmb{F}\cdot \pmb{dll}

    In Chapter 3 a discussion about gravitational energy potential was presented. For example, for the gravity force is

    \[ \label{ene:eq:gravity}
    F = - \dfrac{G\,M\,m}{r^2}
    \] Where \(G\) is the gravity coefficient and \(M\) is the mass of the Earth. \(r\) and \(m\) are the distance and mass respectively. The gravity potential is then

    \[ \label{ene:eq:gavityPotential}
    PE_{gravity} = - \int_{\infty}^r - \dfrac{G\,M\,m}{r^2} dr
    \] The reference was set to infinity. The gravity force for fluid element in small distance then is \(g\, dz\, dm\). The work this element moving from point 1 to point 2 is

    \[ \label{ene:eq:eleGravity}
    \int_1^2 g\, dz\, dm = g\,\left(z_2 - z_1 \right) dm
    \] The total work or potential is the integral over the whole mass.

    Contributors and Attributions

    • Dr. Genick Bar-Meir. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or later or Potto license.