Work, Power and Simple Machines
Machines Make work easier to do by: Increasing the size of an applied force Changing the direction of an applied force Changing the distance over which a force acts There will always be a trade-off!!!
Sketch, label, and describe each different method. Challenge: Create three machines to lift the mass in three different ways http://physics.fau.edu/observatory/Images/100gmass.jpg Use the following materials: Ruler Marker tape http://finepointdesign.com/wp-content/uploads/2011/01/DSC05618_markers_web.jpg http://www.pencils.com/sites/default/files/imagecache/product/Color_Rulers.jpg http://27.media.tumblr.com/tumblr_lhs14t9rhm1qzur0wo1_400.jpg
The Six Simple Machines pulley lever inclined plane http://cnx.org/content/m23853/latest/ http://www.the-office.com/summerlift/pulleybasics.htm http://www.schnauzerlover.com/ramp.htm screw wheel & axle wedge http://www.g9toengineering.com/resources/simplemachines.htm http://en.wikipedia.org/wiki/Ferris_wheel http://makeitgo.wikispaces.com/wedges
Some machine basics… Input output What goes in… http://tech.texasdi.org/simplemachines http://elimeirkaplan.com/blog/?p=608 Output is also called “resistance:” Resistance force is the force exerted by a machine Resistance distance is the distance across which the machine applies effort Input is also called “effort:” Effort force is the force applied to a machine Effort distance is the distance across which the effort is applied output What comes out…
Levers LOAD EFFORT FULCRUM The mass being lifted by a lever Force used to lift the load FULCRUM Fixed point about which the lever rotates Review: Force is a push or a pull on an object, and is measured in Newtons
1st Class Lever RESISTANCE DISTANCE… EFFORT DISTANCE… FULCRUM… is between the effort and the load
Your experiment… Use the following materials: Ruler Marker Tape Explore the relationship between effort force required to lift a load, and the length of the resistance distance. Use the following materials: Ruler Marker Tape Spring Scale 100-g mass Resistance Force = ____ N
Your experiment… Data Collection: - repeat for 3 trials at this fulcrum position for consistency - average the effort needed for this fulcrum position Data Table 1: Effort force measurements for fulcrum positioned at ____ cm Trial Fulcrum Position (cm) Resistance Distance(cm) Effort Force (N) 1 2 3 Average
Ideal Mechanical Advantage Actual Mechanical Advantage Number of times the input is increased by a machine Ideal Mechanical Advantage The mechanical advantage in a “perfect” world; predicted mechanical advantage Actual Mechanical Advantage The real mechanical advantage that results when the machine is in use
Summarize your findings What did you determine, through your experiment, about the relationship between the (length of the) resistance arm and the effort needed to lift the load?