12/2/08

Post date: Dec 02, 2008 3:42:41 AM

Bell Activity: Describe the changes in energy as a skiier skis down a slope.

• • Energy Flow diagrams

    • Tool to visualize path of energy

    • ALWAYS branch out because no energy transfer is 100% efficient

    • Can almost always be traced back to the sun

    • Example: EFD for skiier going down slope

    • Practice: Draw an EFD for Tom Hanks making a fire in Castaway

  • Collisions

    • Can be elastic, inelastic, or somewhere between

      • inelastic = objects collide and stick together

      • elastic = objects collide without deforming, mechanical energy is conserved (no energy goes to heat)

      • between = objects collide and deform some, so some of the mechanical energy goes to heat

    • For elastic collisions, we use conservation of energy AND conservation of momentum to learn outcomes of collision

      • Example: A 7 kg bowling ball moving to the right at 2 m/s collides elastically with a 9 kg bowling ball moving at 1 m/s to the left. Find final velocity of each bowling ball.

    • For inelastic and partially elastic collisions, we can find out how much energy goes to deforming and heating the objects

      • Example: Page 234 car crash

  • Page 234: 13-16 Due Wednesday