Fluids and Motion

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Fluids and Motion

• Pressure Refers to a force pushing on a
  surface. Area is the measure of a surface.
• Calculating Pressure Pressure (Pa) Force (N)
• Area (m2)
• Pressure is equal to the force exerted on a
  surface divided by the total area over which the
  force is exerted.
• Pascal The SI unit for pressure
• 1 Pascal (Pa) 1 N
• m2

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Fluids and Motion

• 5. Fluids A substance that can easily flow.
  Fluids are able to change shape. Liquids and
  gases are fluids.
• 6. Fluid Pressure All the forces exerted by the
  individual particles (atoms, molecules) in a
  fluid add together to make up the pressure
  exerted by the fluid.
• 7. Fluid Pressure All Around Air exerts
  pressure because it has mass. 1 cubic meter of
  air has a mass of 1 kg. Gravity pulls on this
  mass gives air a pressure.

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Fluids and Motion

• 8. Balanced Pressure Average air pressure at
  sea level is 10.13 N/cm2. Why arent you crushed
  by this pressure?
• 9. Pressure Elevation Air pressure decreases
  as elevation increases. At higher elevations
  there is less air for gravity to pull on,
  therefore the weight of the air is less. As the
  air pressure decreases your ears pop. Why?

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Fluids and Motion

• 10. Pressure Depth Water pressure increases
  as the depth of the water increases. Water
  pressure is due to the weight of the water above
  a particular point. Also air in the atmosphere
  pushes down on top of the water. Therefore when
  one is under water, the total pressure you are
  under is equal to the weight of the water plus
  the weight of the air above you. In the
  deepest parts of the ocean the pressure is 100x
  the air pressure you experience daily.

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Motion Pressure in Fluids

• 11. Pascals Principle When a force is applied
  to a confined standing fluid, an increase in
  pressure is transmitted equally to all parts of
  the fluid.

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Motion Pressure in Fluids

• 12. Force Pumps Increased pressure at one end
  of a fluid in a container with a hole at the
  other end. Because the fluid is not confined by
  the container the fluid is pushed out of the
  opening. Ex. The Human Heart Two force pumps -gt
  One pumps blood to the lungs to pick up oxygen.
  The oxygenated blood returns to the heart and is
  sent to the rest of your body by the second pump
  

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Motion Pressure in Fluids

• Hydraulic Systems Designed to take advantage of
  Pascals Principle -gt A hydraulic system
  multiplies a force by applying the force to a
  small surface area. The increase in pressure is
  then transmitted to another part of a confined
  fluid which pushes on a larger surface area.
• Ex.s Disc Brakes of a Car
• Sea Starfish Movements

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Motion Pressure in Fluids

• 14. Hydraulic Systems

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Floating and Sinking

• 15. Buoyancy Water exerts a buoyant force which
  acts in an upward direction against the force of
  gravity. So an object will feel lighter in water
  than in air.

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Floating and Sinking

• 16. Archimedes Principle states that the
  buoyant force on an object is equal to the weight
  of the fluid displaced by the object.
• 17. Density Mass/Volume -gt An object that is
  more dense than the fluid in which is immersed
  sinks. An object that is less dense than the
  fluid in which it is immersed floats to the
  surface.

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Floating and Sinking

• 18. Buoyancy and Density an object with a
  lighter density floats easily and is said to be
  more buoyant.
• 19. Buoyancy - A larger object will displace more
  fluid. This increases the buoyant force on the
  object. Ex. A large ship displaces a lot of
  water also the ship is filled with air which
  is less dense than water.

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Flight

• 20. Bernoullis Principle States that the
  pressure exerted by a moving stream of fluid is
  less than the pressure of the surrounding fluid.
• Ex.s would be airplane wings or a birds wings
  The top of the wing is curved, this forces the
  air to travel faster over the top of the wing.
  Thus the air pressure is less above the wing
  (Bernoullis Principle). The higher air pressure
  from the slower moving air beneath the wing
  forces the wing upward.

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Flight

• 21. Objects in Flight Bernoullis Principle

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Flight

• 21. Spoilers on Race Cars Upside down wings
  Bernoullis Principle -gt The higher air pressure
  of the slower moving air above the wing pushes
  the car down onto the track. The exact opposite
  of what occurs with an airplanes wings.