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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
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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).
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.
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 decreases http://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?