12/3/08

Post date: Dec 03, 2008 1:8:49 AM

Bell Activity: Why do your ears sometimes "pop"?

• • Fluids

    • Gases and liquids are both fluids

    • Pressure

      • P = F/A

      • Units are N / m^2 or Pascals

      • Atmospheric pressure is 101,000 Pascals or about 14.7 pounds per square inch

      • The pressure in our body pushes out the same amound, so we don't get squished.

        • If this changes, we feel it in our ears (ears pop)

        • In space, there is no (or almost no) pressure, so our internal pressure pushes out on our bodies ... Ouch!

    • Buoyant Force

      • All fluids exert an upward buoyant force on matter

      • Archimedes' Principle - amount of buoyant force is equal to the weight of the fluid that is displaced by the object

      • Objects float or sink based on density

    • Pascal's Principle

      • The pressure is equal in all parts of an enclosed fluid.

      • P1 = P2 = P3 = P4 = ...

      • Hydraulic devices use Pascal's principle

        • Apply a small force over a certain area of the fluid

        • Output to a larger area, creating a larger output force

        • Page 93 Practice problem

    • Fluids in motion

      • Fluids speed up to go through a smaller area.

        • Ex. Rivers run faster through narrow canyons

        • Ex. Cover part of a hose opening with your thumb to make the water move faster and shoot farther

      • Viscosity

        • Viscosity is a liquid's resistance to motion (the opposite of runniness)

        • Water has low viscosity, maple syrup and honey have higher viscosity

      • Bernoulli's Principle

        • The pressure in a fluid decreases as the fluid's speed increases

          • Light objects in your car tend to fly out open windows

          • Blow over the top of a piece of paper and it lifts upward

• Page 93:1 due tomorrow

  • Also include answers to these questions:

    • • Describe Pascal's Principal.

      • Explain how Pascal's Principal is related to question 1 (or how it's being applied)