If a person studies about a fluid which is at rest, the study is called:
Try it first: pick an option, then read the explanation.
Correct answer: D. fluid statics
Asked in SSC JE 10/10/2023 (10am-12pm)
Detailed Explanation
When a fluid is at rest, no shear stress can exist within it because fluids continuously deform under even infinitesimal shear forces. The branch of engineering mechanics that studies fluids in this state of static equilibrium is fluid statics.
Why “fluid statics” Is Correct
By definition, fluid statics (or hydrostatics for liquids) is the science of fluids at rest, where all internal stresses are purely normal compressive pressures.
Why the Other Options Are Wrong
- A. fluid kinematics: Fluid kinematics studies fluids in motion without regard to the forces causing motion.
- B. fluid mechanics: Fluid mechanics is the broad subject covering both fluids at rest and in motion.
- C. fluid dynamics: Fluid dynamics studies fluids in motion considering the acting forces and energy exchanges.
Key Point
Fluid statics deals with fluids at rest; shear stresses are strictly zero.
Key Concepts for Students
- In fluid statics, shear stress τ = 0 throughout the fluid.
- Pressure at any point in a static fluid is isotropic (equal in all directions, Pascal's law).
- Pressure variation in static fluid depends solely on vertical depth: dp/dz = -ρg.
Practice more: this is question 12 in Properties of Fluid MCQs – Part 1. Try the whole set and check every answer instantly.