A fluid, unlike a solid is a
substance that can flow. Fluids can be of two types liquids or gases.
The difference between a liquid and a gas is the positioning of the
molecules. In gases the molecules are much farther apart than a liquid.
This does not prevent either substance from flowing. Unlike solids where
mass and the amount of force exerted on the mass controls the motion,
fluids move in response to density and pressure.
The following are some of the
fundamental principles that will be observed in lab. You may want to use
examples to illustrate these principles. In lab, we will not ask
students to figure out which principle applies to the different
stations, because often there is a combination of principles at work.
The lab will center around observing how fluids move. Stress to students
that pressure within the fluid helps move it. The key objective is to
introduce that fluids have motion just like solids, not to memorize the
A change in the pressure applied to an enclosed container is transmitted
without change throughout the fluid and acts in all directions.
Archimedes' Principle. A body
immersed in a fluid will be buoyed up by a force equal to the weight of
the fluid that it displaces.
The pressure in a fluid decreases with increased velocity of the fluid.
(The faster the liquid moves, the lesser is the pressure in that