MCAT Fluid Dynamics Flashcards
Density. What’s the density of water?
The ratio of mass over volume. SI unit is Kg/m^2.
Density of water is 1 kg/L.
Specific gravity ( SG)
The relative density of two substances.
Found by divided the density of one substance by the density of water.
Pressure
The perpendicular force applied to an area.
The SI unit is the pascal where 1Pa = 1N/m^2
Hydrostatic pressure
The pressure exerted by a fluid.
Atmospheric pressure
The pressure exerted by gas molecules.
Simple fluid barometer
A device used to measure atmospheric pressure.
The atmospheric pressure applies a force perpendicular to the area which causes mercury to rise in the barometer. Therefore, the atmospheric pressure equals the hydrostatic pressure.
Pascal’s law
Law that states that when a pressure is exerted to a closed system it moves uniformly throughout that system.
Archimedes principle
Describes the buoyant force.
The buoyant force is constant and doesn’t depend on the depth of the submerged object.
The behavior of the object depends on the densities of the two objects.
What happens when an object floats, submerged, and sinks?
When object floats the density of the object is less than the density of the fluid. The weight of the object is less than the buoyant force.
When an object is submerged the object’s density is equal to the fluid’s density. The weight of the object is equal to the buoyant force.
When an object sinks the density of the object is greater than the density of the fluid. The weight of the object is greater than the buoyant force.
How do we apply Archimedes principle?
The apparent weight of the object is different in air vs. water.
The apparent weight of an object is greater in air than in water.
What are the two intermolecular forces experienced by water?
Cohesive forces are intermolecular forces between the same molecules and are responsible for holding the liquid together.
Adhesive forces are intermolecular forces between different molecules.
What creates surface tension of a liquid?
In the center of the molecules the net cohesive force is zero because it’s surrounded by other similar molecules. At the periphery it’s the molecules experience a force inward.
Surface tension acts to decrease surface area so greater the surface tension the less the surface area.
How does water acts as an elastic membrane?
Water has a restoring force so that when an object lands on the surface the force acts to minimize the surface area.
What causes capillary action to occur?
When adhesive forces overcome surface tension is moves up the tube.
Describe the difference between ideal fluids and nonideal fluids
Ideal fluids experience no viscosity (viscosity is the resistance of flow due to friction between molecules of the fluid), they’re incompressible (density is constant and independent of the pressure applied), they also exhibit laminar flow (smooth flow in parallel lines).
Nonideal fluids experience viscosity are compressible, and exhibit turbulent flow.
