11/18/09

Post date: Nov 18, 2009 2:38:23 PM

Bell Ringer: How can a pulley help us do work?

• • Conferences tonight!

  • Notes - simple machines (finish 13.1, begin 13.2)

    • Machines and mechanical advantage

      • Machines help do work by changing the size or direction of a force

      • The amount that a machine can change a force is described as mechanical advantage.

      • To calculate MA (mechanical advantage), use the equation MA = output force / input force (example: If you apply 5 N of force to a lever, and the lever then applies 10 N of force to the object you want to lift, the MA is 10 / 5, or 2). MA does not have any units

    • Simple machines

      • There are six types of simple machines, divided into two families

        • Lever Family

          • Simple lever - teeter totter, hammer

          • Pulley - cable pulleys, gears

          • Wheel and axle - steering wheel, screw driver

        • Inclined Plane Family

          • Simple inclined plane - ramp, hill

          • Wedge - axe, knife, doorstop, point of a nail

          • Screw - drill bit, screw, spiral staircase, winding mountain road

  • Rube Goldberg Machines

    • Watch video

  • Design your own Rube Goldberg Machine

    • • Designed to accomplish some simple, everyday task

      • Draw out and describe each step

      • Must have at least 10 steps

      • Must include at least 4 of the 6 simple machines, clearly labeled

      • Build your machine and take pictures or video to share with the class for extra credit.