1/27/11

Post date: Jan 27, 2011 5:35:54 PM

• • Bell Ringer: A person in water displaces 165 pounds of water. How much buoyant force will they feel?

  • Fluids through openings

    • • when fluids move from a wide to a narrow opening, they have to speed up to get all the fluid through

      • When fluids move from a narrow to a wide opening, they slow down.

      • example: putting your thumb over part of a hose's opening to shoot water faster and farther

      • example: narrow opening at end of a squirt gun to make water shoot faster and farther

      • example: clear tape over most of sink opening to shoot water fast and get user wet (good April Fool's prank!)

Pressure and movement

• • Fluids generally move in ways that will equalize pressure differences

  • Fluids flow from higher pressure to lower pressure (higher pressure side is pushing them harder than the lower pressure side)

  • Objects in a fluid will move with the fluid according to pressure differences

  • example: Fire One! game (push on pumps to move plastic piece using air pressure)

  • example: Compressed air leaking out of a tire into the lower pressure atmosphere

  • example: Hiss when opening a soda due to higher pressure air (and CO2) inside bottle moving into lower pressure atmosphere.

  • example: ALL WEATHER is driven by differences in pressure

• P.94: 1-9 due tomorrow

  • Planes and paper planes

    • For tomorrow, you MUST know how to make a paper airplane ... have someone teach you if you don't know how!