9/10/09

Post date: Sep 11, 2009 1:5:26 PM

Bell Ringer: What is needed for a solid to turn into a liquid or a gas?

• • Oobleck presentations

• 3.3 Notes

  • 3.3 Demos

    • Pressure

      • Balloon pops on one nail in a board, but not on the bed of nails because the force is spread over a bigger area, making less pressure

      • Mr. Bennett can lie on the bed of nails without being hurt because his weight is spread over a bigger area - less pressure

      • The air around us exerts pressure on us. A bottle of water with a single hole in the bottom will not leak because the pressure inside the bottle is equal to the pressure outside the bottle. When the bottle is squeezed, there is more pressure inside than out, so water comes out the hole.

    • Bernoulli's Principle

      • A ping pong ball floats on a jet of air from a compressor, hair dryer, or straw. The fast-moving air has lower pressure than the still air around it, which sucks the ping pong ball in.

      • Blowing out through a funnel will capture a ping pong ball for the same reason.

    • Pascal's Principle

      • Two connected bottles are filled with water. The bottom bottle has holes poked in it. When the top bottle is squeezed, water shoots out of each hole at the same time with the same force. The pressure in the top bottle is transferred evenly throughout the bottle, making water come out everywhere at the same time.

• Page 94: 1-9 due tomorrow