ERTH 430:Fluid Dynamics in Earth Systems |
Pre-class Quiz #1:
Continuum Hypothesis, Flow Distortion, and Solving the Governing Equations |

This is a "preview" version of Pre-class Quiz #1. The
preview version is suitable for printing and leisurely inspection before you
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is, the real thing. When you feel ready to submit your answers, go to iLearn's
ERTH 430 "Pre-class Quizzes" section, select the interactive
version, and follow its instructions.

(*Responses must be submitted via iLearn by 9 a.m. on Wednesday, Aug.
30*.

**Description:** The questions below are based on Reading
Assignment #1.

**Questions:**

**(1) Multiple Choice. What** is the *continuum hypothesis*, on which the governing equations for fluid dynamics are based? *(Pick the one best answer.)*

- The assumption that fluids consist of discrete (separate) bits of matter (such as molecules), idealized as infinitesimal points of mass.
- The assumption that the properties of a fluid (such as its temperature, density, and velocity) are spatially continuous (not discrete) within the fluid.
- Mass (matter) can be neither created nor destroyed, but instead is "conserved".
- At any particular point within a fluid, the fluid for all practical purposes can be treated as if it extends indefinitely, without bounds.

**(2) Multiple Choice. When** forces associated with stress (that is, forces that act on the surface of an object) vary from one part of the object's surface to another, the object can undergo *distortion*. What are the two types of distortion?* (Pick the one correct answer.)*

- Changes in the volume of the object (expansion/inflation or compression), and shear.
- Convergence or divergence of the surface of the object, and shear.
- Rotation of the object's orientation in space (spinning) due to torque applied to the object, and changes in the volume of the object (expansion/inflation or compression).
- Changes in the length of the object along any particular axis or dimension (extension/elongation or contraction), and shear.

**(3) Multiple Choice. What** information (constraints, conditions) must we specify as part of solving the governing equations to forecast/predict the future state of a fluid?* (Pick the one correct answer.)*

- The volume and shape of the fluid at some starting time.
- The mass and velocity of the fluid at some starting time.
- The initial (starting) state of the fluid, and the conditions that must be met on the solid and gaseous boundaries of the fluid.
- The recent history of the fluid's behavior leading up to the current time.