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Q: The pressure intensity is same in all directions at a point in a fluid
  • A. Only when fluid is frictionless and incompressible
  • B. Only when fluid is frictionless and is at rest
  • C. Only when fluid is frictionless
  • D. When there is no relative motion of one fluid layer relative to other
Correct Answer: Option B - Pascal's law– Intensity of pressure at any point in a fluid at rest is same in all the directions. (i) Viscosity of fluid has no effect on fluids at rest, therefore ideal and real fluids behave in a similar manner. (ii) If the fluid is in motion, shear stresses occur and normal stresses are no longer same in all directions at a point of a real fluid. (iii) If the fluid is in motion and fluid is ideal (frictional less) then no shear stresses, hence the pressure at any point is same in all the directions.
B. Pascal's law– Intensity of pressure at any point in a fluid at rest is same in all the directions. (i) Viscosity of fluid has no effect on fluids at rest, therefore ideal and real fluids behave in a similar manner. (ii) If the fluid is in motion, shear stresses occur and normal stresses are no longer same in all directions at a point of a real fluid. (iii) If the fluid is in motion and fluid is ideal (frictional less) then no shear stresses, hence the pressure at any point is same in all the directions.

Explanations:

Pascal's law– Intensity of pressure at any point in a fluid at rest is same in all the directions. (i) Viscosity of fluid has no effect on fluids at rest, therefore ideal and real fluids behave in a similar manner. (ii) If the fluid is in motion, shear stresses occur and normal stresses are no longer same in all directions at a point of a real fluid. (iii) If the fluid is in motion and fluid is ideal (frictional less) then no shear stresses, hence the pressure at any point is same in all the directions.