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.