Under what condition will the normal stress at a point in a fluid remain uniform in all directions__________________________?
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Answer: E. it is at rest
Explanation
When a fluid is at rest, shear stresses are zero, meaning the normal stress is isotropic and uniform in all directions. Stationary fluid molecules do not experience relative sliding motion, eliminating directional frictional stress variations. Hydrostatic pressure conditions ensure that pressure measured at any specific point acts equally across all spatial planes. Fluid statics studies fluids at rest, establishing foundational pressure laws for engineering design applications. The absence of velocity gradients in stationary fluids guarantees that shear viscosity terms vanish from equations. Isotropic stress states form the mathematical basis for deriving Pascal's principle in fluid mechanics.
Option A specifies incompressibility, but rest condition is the fundamental physical requirement for isotropic stress. Option B refers to uniform viscosity, which does not eliminate shear stresses if fluid motion is present. Option C specifies zero viscosity, but even viscous fluids exhibit uniform normal stress when completely at rest.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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