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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.

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Presentation on theme: "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."— Presentation transcript:

1 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 mv 3

4 3  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/s 2 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

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) 1 ST CLASS LEVER: FULCRUM IN MIDDLE (“F”) MULTIPLES FORCE OR DIRECTION AND CHANGES DIRECTION EXAMPLE: SEE-SAW 2 ND CLASS LEVER: RESISTANCE (OBJECT) IN THE MIDDLE (“R”) MULTIPLES FORCE WITHOUT CHANGING DIRECTION EXAMPLE : WHEEL BARROW, RAKES 3 RD 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  TOTAL IDEAL MA : PRODUCT OF ALL SIMPLE MACHINES. WHICH MAKE IT UP  GEAR SYSTEM: AN EXAMPLE OF A COMPOUND MACHINE SIMPLE MACHINES IN THE HUMAN BODY  FOREARM: EXAMPLE OF 3RD CLASS LEVER  BALL OF FOOT: A 2ND CLASS LEVER  NECK: A FIRST CLASS LEVER  INCISORS: TEETH WHICH FUNCTION AS WEDGES

13 ROSIE, IRON WORKERS, WELDER, MIGRANT WORKERS, SINGER MACHINE, SIMPLE MACHINES, BIKE, INPUT/OUTPUT, Effort/load, See/saw, Pulley, SIMPLE MACHINES, INCLINED PLANE: SCREW:http://discover.edventures.com/images/termlib/s/screw/support.gifhttp://discover.edventures.com/images/termlib/s/screw/support.gif LEVER: PULLEY: WHEEL: ROTATE LEVER: LEVERS: WEDGE: SCREWS: TRUCK RAMP: SCREWS: SISSORS:


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