Which statement best describes Pascal's Law?

• A. Pressure changes cause no flow in a confined fluid
• B. Pressure changes propagate instantaneously along the fluid surface
• C. Pressure applied to a confined fluid is transmitted equally in all directions
• D. Pressure cannot be transmitted through liquids

Answer: (C)

Pressure applied to a confined fluid is transmitted equally in all directions. This is Pascal’s Law: when you push on a trapped, incompressible liquid, the resulting pressure spreads uniformly throughout the entire fluid and to the container walls. That uniform pressure is what allows a small piston to generate a larger force on a bigger piston, since force equals pressure times area.

In a practical sense, the pressure signal travels through the liquid very rapidly (approaching instantaneous behavior for most engineering purposes), but it does propagate as a pressure wave at the speed of sound in that liquid, not literally instant in every moment.

The other statements describe situations that don’t match how pressure behaves in a confined liquid: pressure changes aren’t inherently tied to stopping flow, pressure isn’t limited to spreading only along a surface, and liquids absolutely do transmit pressure.