11/23/09

Post date: Nov 23, 2009 2:39:54 PM

Bell Ringer: In science what does it mean to say that energy is conserved?

- Review ch. 13 material
  - Work
    - W = Fd
    - Amount of energy used to move something
    - force and motion must be in same direction
    - measured in J
  - Power
    - P = W / t (work divided by time)
    - Amount of energy changing forms in a certain time period
    - measured in watts
  - Mechanical Advantage
    - MA = output force / input force
    - MA = input distance / output distance
    - Ratio that describes how much a machine changes the force you put in
    - Machines with large MA amplify a force greatly
  - Simple Machines
    - Lever Family
      - Simple Lever
      - Pulley
      - Wheel and axle
    - Inclined plane family
      - Simple inclined plane
      - Wedge
      - Screw
    - When simple machines are connected together, we call it a complex machine.
  - Energy
    - Energy is ability to do work
    - Measure in Joules (J)
    - Potential Energy
      - energy of position, caused by gravity
      - PE = mgh
    - Kinetic Energy
      - energy of motion
      - KE = 1/2 m v^2
    - Other forms of energy
      - heat
      - light
      - sound
      - electro-magnetic
      - chemical
      - nuclear
  - Conservation of energy
    - Energy can neither be created nor destroyed, but it changes forms readily
  - Efficiency
    - Percent of energy transferred from one form to another
    - efficiency = (useful energy output) / (energy input)
    - Efficiency is always less than 100%, some energy always goes to heat due to friction
- Chapter 13 review game
- Chapter 13 review assignment
  - Page 466-467: 1-25 (pick 15 for credit, more for extra credit)
  - Due tomorrow