4/9/09
Post date: Apr 09, 2009 12:15:5 AM
Bell Ringer: What is a machine?
Machines
Change the amount or direction of a force needed to do work
Pulley Lab - Due Friday
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%
HW: Page 210: 12-13