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)