Hydrostatic pressure is defined as pressure arising from the weight of fluid above.

• A. From the weight of the fluid above
• B. From viscosity
• C. From surface tension
• D. From diffusion

Answer: (A)

Hydrostatic pressure is the pressure exerted by a fluid at rest due to gravity pulling on the fluid above a given point. The deeper you go, the more fluid sits above, so the weight pressing down increases, making pressure rise with depth. This relationship is captured by P = ρ g h, showing how density, gravity, and depth combine to produce the pressure. Viscosity describes how resistant a fluid is to flow, not the static pressure generated by the weight of the fluid. Surface tension is the cohesive force at a liquid’s surface, important at small scales and interfaces, but it does not set the overall hydrostatic pressure in the bulk fluid. Diffusion involves the spreading of particles due to concentration differences, not the pressure from overlying fluid. So the statement that hydrostatic pressure arises from the weight of the fluid above is the correct description.