Concepts of Physics
Chapter 10
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Updated 2.8.2008

Friday, February 8

  • Ch. 9 & 11 Test
  • Read Chapter 10
  • Next time questions: shaking the berries
  • CG seat - how does it work?

Monday, February 11

  • All about center of gravity
    • Center of gravity is located at an object's average position of weight.
  • Demonstrations: Happy Apple, leaning tower of Pisa, plastic eagle, fork and cork, popcorn box
  • Leaning tower of Pisa information link 1 | link 2 | link 3
    • Construction began in 1173 and took 200 years to get to its current height. Lean distance by year: 1298: 1.43m, 1550: 3.77m, 1817: 3.84m, 1997: 5.20m
    • See a full size image of the tower
  • Stable objects
  • Stability occurs for standing objects (people, buildings, etc.) when the center of gravity is within and above the area of support.
  • Stability occurs for hanging objects when the center of gravity is located directly below the point of support.
  • Toppling
    • How this relates to vehicle rollover
    • Demonstrations:
      • Male vs. female pick up chair with head touching wall and legs vertical.
      • Sit on chair and get up slowly; keep your hands on your knees and feet perpendicular to the floor.
      • Stand with the back of your heel against a wall and try to touch your toes
      • Why do pregnant women get back pains?
      • Right shoulder, right foot against wall. Hold left leg up in air.

    • Tuesday, February 12 – Juniors taking PSSA Writing test today

    Wednesday, February 13 – No school – Snow Day

    Thursday, February 14

    • Center of Gravity Lab (in class activity)
      • wheels with offset weight
      • finding center of gravity of a meterstick
      • finding the center of gravity of an irregular object
      • finding your center of gravity
      • rolling uphill

    Friday, February 15 – No School – Teacher Professional Development Day

    Monday, February 18

    • Go over center of gravity lab
      • Difference between men and women
    • Center of mass can be outside of center of gravity for a multiple object system like the solar system. If all planets are aligned, the center of mass is outside the sun. If the planets are scattered evenly then the center of mass of the solar system is near the center of the sun.
    • CG of tall buildings
    • CG of boomerangs
    • Toppling (if the CG is above the area of support the object will remain upright)
      • How this relates to vehicle rollover
    • Animals use tail to change CG while moving to keep their balance; acrobats use a pole to keep CG.

    Tuesday, February 19