SC7 Unit 2 lessons 1-2-3: Work and Simple Machines

1. SC7 Unit 2 lessons 1-2-3: Work and Simple Machines • LESSON 1: WORK, ENERGY AND POWER • WORK: THE USE OF FORCE TO MOVE AN OBJECT • BOTH FORCE & MOTION MUST BE IN THE SAME DIRECTION • EQUATION: WORK = FORCE x DISTANCE • UNITS OF WORK : 1 NEWTON * 1 METER = 1 JOULE (1 Nm)

2. ENERGY: THE ABILITY TO DO WORK • ENERGY IS NECESSARY TO DO WORK • UNITS OF ENERGY – SAME AS UNIT OF WORK : JOULES (j) • WORK TRANSFERS ENERGY TO AN OBJECT • POWER: HOW FAST WORK IS DONE • EQUATION: ENERGY ÷ TIME • UNITS OF POWER: JOULE PER SECOND (JOULE/SEC) = 1 WATT • NAMED AFTER JAMES WATT (STEAM ENGINES, 1800’S) • 1 HORSEPOWER = 746 WATTS

3. LESSON 2: KINETIC AND POTENTIAL ENERGY • KINETIC ENERGY (KE): THE ENERGY OF MOTION (measured in joules) • ALL MOVING OBJECTS OR MOLECULES HAVE KINETIC ENERGY • KINETIC ENERGY DEPENDS ON MASS AND SPEED • EQUATION: ½ mv3

4. POTENTIAL ENERGY (PE): STORED ENERGY (measured in joules) • POTENTIAL ENERGY HAS THE ABILITY TO DO WORK • TYPES OF POTENTIAL ENERGY • GRAVITATION POTENTIAL ENERGY BASED ON HEIGHT • GPE = mass x 9.8 m/s2 x height (gpe = m*g*h) • GREATER HEIGHTS RESULT IN GREATER gpe. • ELASTIC POTENTIAL ENERGY STORED IN STRETCHED OBJECT • MECHANICAL POTENTIAL (ME) STORED IN POSITION • NOT HEIGHT ABOVE GROUND (gpe) • EQUATION: ME = KE + PE • CHEMICAL POTENTIAL STORE IN BONDS BETWEEN ATOMS 3

5. MACHINES: DEVICES THAT MAKE WORK EASIER • MACHINES CAN CHANGE SIZE OF FORCE, DIRECTION OF FORCE, & DISTANCE OF FORCE • SIMPLE MACHINES MAKE UP MACHINES • SIMPLE MACHINES MAKE WORK EASIER WITH A SIMPLE MOTION • 6 SIMPLE MACHINES: RAMPS, LEVERS. WHEELS/AXLES, SCREW, WEDGES, PULLEYS • MACHINES CAN MULTIPLE FORCE OR MULTIPLE DISTANCE • CANNOT DO BOTH AT THE SAME TIME • FORCE MULTIPLIED FORCE AT THE COST OF LONGER DISTANCES • DISTANCE MULTIPLIED AT THE COST OF GREATER FORCES • CAN NEVER MULTIPLY WORK

6. MECHANICAL ADVANTAGE: INDICATES HOW FORCE (OR DISTANCE) IS MULTIPLIED • MA = 1: DISTANCE MULTIPLIED • MA > 1 FORCE MULTIPLIED • MA < 1 DISTANCE MULTIPLIED • MA EQUATION: MA = OUTPUT FORCE ÷ INPUT FORCE • OUTPUT FORCE: FORCE DONE BY THE MACHINE • INPUT FORCE: FORCE YOU PUT INTO MACHINE

7. MECHANICAL EFFICIENCY: INDICATES HOW MUCH WORK IS LOST TO FRICTION • ME IS ALWAYS A PERCENTAGE LESS THAN 100% (FRICTION ALWAYS PRESENT) • ME EQUATION: ME = (WORK OUTPUT ÷ WORK INPUT ) x 100 • WORK OUTPUT: WORK DONE BY THE MACHINE • WORK INPUT: WORK YOU PUT INTO A MACHINE

8. THE 6 TYPES OF SIMPLE MACHINES 1. LEVER: A BAR THAT PIVOTS ON A FULCRUM (THE PIVOT POINT OF A LEVER) 1ST CLASS LEVER: FULCRUM IN MIDDLE (“F”) MULTIPLES FORCE OR DIRECTION AND CHANGES DIRECTION EXAMPLE: SEE-SAW 2ND CLASS LEVER: RESISTANCE (OBJECT) IN THE MIDDLE (“R”) MULTIPLES FORCE WITHOUT CHANGING DIRECTION EXAMPLE : WHEEL BARROW, RAKES 3RD CLASS LEVER: EFFORT IN THE MIDDLE – YOU – (“E”) MULTIPLIES DISTANCE WITHOUT CHANGING DIRECTION USED TO MULTIPLE THE MOMENTUM TRANSFERRED TO OBJECTS IN SPORTS EXAMPLES: BASEBALL BATS, GOLF CLUBS, HAMMERS

9. 3. WHEEL AND AXLE: A LARGER WHEEL THAT TURNS A SMALLER SHAFT • MA OF A WHEEL & AXLE THE RESULT OF THE THEIR SIZE DIFFERENCE • MA = RADIUS OF INPUT (WHEEL) ÷ RADIUS OF OUTPUT (SHAFT) • LARGER WHEELS CREATE GREATER MA • 4. INCLINED PLANES: A SLANTED, FLAT SURFACE ( A RAMP ) • LONGER RAMPS HAVE A GREATER IDEAL MA • LESS FORCE BUT LONGER DISTANCES • FRICTION REDUCES THE ACTUAL MA OF RAMPS • IDEAL MA OF A RAMP = RAMP LENGTH ÷ RAMP HEIGHT

10. 5. WEDGES: A MOVABLE SINGLE OR DOUBLE INCLINED PLANE LONGER, THINNER WEDGES HAVE GREATER IDEAL MA EXAMPLES: HAMMER CLAW, CHISEL, KNIFE EDGE 6. SCREW: AN INCLINED PLANE WRAPPED AROUND A CYLINDER THREADS: THE TERM FOR THE RIDGES ON A SCREW CLOSER THREADS HAVE GREATER IDEAL MA

11. 3. PULLEYS: A GROOVED WHEEL AND AXLE HOLDING A LINE OR ROPE • IDEAL MA OF A PULLEY SYSTEM EQUALS THE # OF LINES HOLDING UP OBJECT • FIXED PULLEYS: ATTACHED TO A STATIONARY OBJECT: CANNOT MOVE • CAN ONLY CHANGE THE DIRECTION OF FORCE • ALWAYS HAVE AN IDEAL MA OF 1 • MOVABLE PULLEY: NOT ATTACHED, FREE TO MOVE UP AND DOWN • MOVING PULLEYS DO NOT CHANGE THE DIRECT OF FORCE • MOVING PULLEYS MULTIPLY FORCE AT THE COST OF LONGER DISTANCES • PULLEY SYSTEMS (BLOCK AND TACKLES) COMBINE FIXED AND MOVING PULLEYS • PULLEY SYSTEMS MAY BOTH CHANGE DIRECT OF FORCE AND MULTIPLY FORCE • PULLEY SYSTEMS MULT. FORCE: MA = # OF LINES HOLDING MOVABLE PULLEY

12. COMPOUND MACHINES: A COMBINATION OF SIMPLE MACHINES • TOTALIDEALMA : PRODUCT OF ALL SIMPLE MACHINES. WHICH MAKE IT UP • GEARSYSTEM: AN EXAMPLE OF A COMPOUND MACHINE • SIMPLE MACHINES IN THE HUMAN BODY • FOREARM: EXAMPLE OF 3RD CLASS LEVER • BALLOFFOOT: A 2ND CLASS LEVER • NECK: A FIRST CLASS LEVER • INCISORS: TEETH WHICH FUNCTION AS WEDGES

13. PICTURES CITED ROSIE, http://users3.ev1.net/~de238/stewart/stewartgraphics/r_riviter.gif IRON WORKERS, http://whyfiles.org/170skyscraper/images/iron_workers.jpg WELDER, http://www.aoe-coe.com/gif/welder.jpg MIGRANT WORKERS, http://www.saludparalagente.org/graphics/migrant_workers.jpg SINGER MACHINE,http://www.antiqbuyer.com/images/sewing%20machine/sing20a.jpg SIMPLE MACHINES, http://www.sirinet.net/~jgjohnso/sixsimplemach.jpg BIKE, http://http://www.jek2004.com/Simple-machines-cover-sketc.jpg INPUT/OUTPUT, http://discover.edventures.com/images/termlib/m/mechanical_advantage/support.gif Effort/load, http://www.dtonline.org/areas/6/1/2/p.gif See/saw, http://library.thinkquest.org/CR0210120/Media/see%20saw Pulley, http://www.sciencetech.technomuses.ca/english/schoolzone/images/fPulley2.GIF SIMPLE MACHINES, http://myschoolonline.com/image/display/local/0,2306,MA-31670,00.gif INCLINED PLANE: http://www.skooltools.com/Agri-Science/Ag%20Mechanics/Images/Inclined%20Plane%20Poster.jpg SCREW:http://discover.edventures.com/images/termlib/s/screw/support.gif LEVER: http://discover.edventures.com/images/termlib/l/lever/support.gif PULLEY: http://discover.edventures.com/images/termlib/f/fixed_pulley/support.gif WHEEL:http://discover.edventures.com/images/termlib/w/wheel/support.gif ROTATE LEVER: http://discover.edventures.com/images/termlib/r/rotary_to_lever_motion/support.gif LEVERS: http://discover.edventures.com/images/termlib/t/third_class_lever/support.gif WEDGE: http://discover.edventures.com/images/termlib/w/wedge/support.gif SCREWS: http://www.yourdictionary.com/images/ahd/jpg/A4screw.jpg TRUCK RAMP: http://www.equipmentandsupply.com/yardramp.jpg SCREWS: http://www.mertons.com/img_content/bronze-screws-2.jpg SISSORS: http://gsn.k12.oh.us/PaintValley/web_page_contest/Final%20Pictures/sissors.jpg http://img.ebigchina.com/cdimg/172748/655213/0/1098606459.jpg http://www.thecei.org.uk/BikeStreet/old-bike.jpg http://www.phys.unsw.edu.au/~jw/graphics/blocks1.GIF http://db.library.queensu.ca/steam/wever/gcldc%20pulleys/Ki%20marina%20pulleys.jpg http://physics.ucsc.edu/~josh/6A/book/forces/img60.gif www.istockphoto.com/file_thumbview_approve/438808/2/istockphoto_438808_wagon_wheel_and_axle http://home.earthlink.net/~ocleide/HW_portrait.jpg http://www.thecei.org.uk/BikeStreet/old-bike.jpg http://muaythaitraining.files.wordpress.com/2007/06/anatomy-of-the-elbow.gif http://www.dental.ufl.edu:1180/Offices/Operative/Faculty_pages/Gordan/images http://www.openerg.com/psz/images/feet.gif http://www.toyourhealth.org.uk/content/image/incisor.gif http://www.tpub.com/content/engine/14037/img/14037_43_2.jpg http://www.unis.org/UNIScienceNet/Bicycle_1.jpg http://upload.wikimedia.org/wikipedia/commons/thumb/b/b7/Pulleys.svg