11/17/08

Post date: Nov 17, 2008 2:36:36 AM

Bell Activity: What is a machine?

    • Machines

      • Change the amount or direction of a force needed to do work

      • Make up for decreased force with increased distance

      • Broken into 2 families of simple machines

        • Lever family

          • Simple levers

          • Pulleys

          • Wheel and Axels

        • Inclined Plane Family

          • Simple inclinded plane

          • Wedge

          • Screw

      • Mechanical Advantage = Force out / Force in

        • Example - A car jack lifts a 500 N student by having another student input a force of 10 N. What is the mechanical advantage of the jack? ----- 50.

      • Efficiency = Work out / work in

        • Example - A car engine does 500,000 J of work moving the car forward, and uses 6,000,000 J of energy from the gasoline. What is the efficiency of the car? ---- .083, or 8.3%

      • MA and efficiency practice due Tuesday (handed out to share or available on web site)