Starter 4/21/14
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Transcript of Starter 4/21/14
Starter 4/21/14
• 1. What is the difference between a solid, liquid, and gas?
• 2. How does a boat float?
Properties of Fluids
2/5/13
Fluids• Flow
• Have no definite shape
• Ex: gasses and liquids
Pressure• Applying force to a surface
• F is perpendicular to A• Unit of measure is pascal (Pa) = 1 Newton per
square meter. Since this is small, we usually see kilopascals (kPa).
P = FA
Pascal’s Principle• The shape of a container has
no effect on the pressure of the fluid it contains at any given depth.
• Any change in pressure applied at any point is transmitted throughout the fluid.
• Ex: squeezing a tube of toothpaste.
Hydraulic Lifts
Buoyant Force• The upward force on an object from the fluid. • If the buoyant force is greater than or equal to
the weight of the object, it will float.
Archimedes Principle• The magnitude of a buoyant force is equal to the
weight of fluid displaced.
• Fish and air bladders
Bernoulli’s Principle• As the velocity of a fluid increases, the pressure
exerted by the fluid decreaseshttp://www.youtube.com/watch?v=P-xNXrELCmU http://www.youtube.com/watch?v=WDGNcmEOjs4
Cohesive Forces• Forces of attraction that particles exert on each
other.
Surface Tension• Tendency of the surface of a liquid to contract to
the smallest possible area.• Top molecules are attracted to the sides and
downward, but not upward.
Adhesion• Attractive force between particles of different
substances.
Capillary Action• Water rises in a glass
tube because the adhesion between glass and water is stronger than the cohesive force of water.
• Water rising upward in soil to plant roots
Evaporation• Fast moving particles on the surface of a
liquid “escape.” – break free of cohesive force.
• Since kinetic energy is lost, evaporation has a cooling effect
• Liquids that evaporate quickly are called volatile liquids (rubbing alcohol)
• Humid days reduce evaporation of our perspiration, so we feel hotter.
Condensation• If the kinetic energy
decreases, particles turn back to a liquid.
• What is the Dew Point on the weather forecast?