Chapter 7 - Some Mathematics:
The Equations of Motion

7.9 Important Concepts

1. Gravity, buoyancy, and wind are the dominant forces acting on the ocean.



2. Earth's rotation produces a pseudo force, the Coriolis force.



3. Conservation laws applied to flow in the ocean lead to equations of motion; conservation of salt, volume and other quantities can lead to deep insights into oceanic flow.



4. The transformation from equations of motion applied to fluid parcels to equations applied at a fixed point in space greatly complicates the equations of motion. The linear, first-order, ordinary differential equations describing Newtonian dynamics of a mass accelerated by a force become nonlinear, partial differential equations of fluid mechanics.



5. Flow in the ocean can be assumed to be incompressible except when de-scribing sound. Density can be assumed to be constant except when density is multiplied by gravity g. The assumption is called the Boussinesq approximation.



6. Conservation of mass leads to the continuity equation, which has an especially simple form for an incompressible fluid.

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