A fluid is defined as any substance that_________________?
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Answer: D. Flows when even a small shear is applied to it
Explanation
A fluid is fundamentally defined by its inability to resist static shear stress without continuously deforming. Even an infinitesimally small shear force applied to a fluid will cause it to flow continuously. This characteristic distinguishes liquids and gases from solid materials that resist shear strain elastically. Solids can maintain a static deformation under applied shear stress, whereas fluids cannot remain at rest under shear. The continuous deformation under shear stress defines the core mechanics of fluid dynamics and rheology. Both liquids and gases fall under the scientific classification of fluids due to this shared mechanical behavior.
Keeping a substance in a closed container is a storage requirement for gases rather than the physical definition of a fluid. Liquids are nearly incompressible, but gases are highly compressible, making incompressibility an incorrect defining trait. Having zero shear stress describes an inviscid fluid at rest rather than the fundamental definition of any fluid.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
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