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8/14/2019 Energy, Work, & Machines
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Energy, Work, &
Machines
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1. EnergyThe ability to do work
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2. There are 2 types of
energy.A.Potential Energy- Stored energy such as a wound spring or
gasoline
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B. Kinetic EnergyEnergy in motion such as a moving car or
flowing water.
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3. ForceA push, pull, or lift.
Measured in newtons (N)
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4. WorkA force put on an object that causes the object
to move a distance.
Work is measured in Joules (J)
Work = Force x Distance
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5. PowerThe amount of work done in a period of time.
The faster work is done, the more power youwill use.
Measured in watts (W)
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6. MachineAny device that makes work easier.
There are 6 simple machines: Lever, Wheel &Axle, Pulley, Inclined Plane, Wedge, Screw
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7. Machines have 4
purposesThey makes work easier
They put a force where we want it
They can make work go fasterThey can make a force larger
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8. LeverA simple machine made up of a rigid bar that is
free to move about a fixed point.
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9. FulcrumThe fixed point of a lever, the point where the
lever balances.
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10. EffortThe force applied to move an object.
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11. Resistance (Load)The force that opposes the effort, or the object
being moved.
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12. There are 3 classes of
levers:
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A. First class leversthe fulcrum is between effort & resistance.
Example: seesaw, scissors, pliers
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B. Second class leverResistance is between the fulcrum and effort.
Example: wheelbarrow, paper cutter,nutcracker
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C. Third class leverEffort is between resistance and fulcrum.
Examples: baseball bat, rake, hockey stick
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13. Mechanical
advantageThe number of times a machine multiplies a
force.
Formula:
MA = Length of Effort arm / Length ofresistance arm
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14. Wheel & AxleA simple machine in which the wheel and axleturn together
MA =diameter of wheel / diameter of axle
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15. GearA wheel with teethWhen gears are meshed together, they turn in
opposite directions.
MA can be calculated by comparing the # ofteeth
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16. PulleyA wheel with a groove that holds a rope orcable.
There are 3 basic types.
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17. Fixed pulleyA pulley that attaches to a structure.It changes the direction of the force but does
NOT multiply the effort.
MA is always 1
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18. Movable PulleyA pulley that attaches to the resistance andmoves as the resistance moves.
MA is always 2
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19. Compound PulleyA combination of fixed and movable pulleys.Used to multiply force and change direction of
force
Example: Block & Tackle
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20. Pulley Mechanical
AdvantageCount the number of ropes supporting the
resistance.
Pulling down is NOT counted as a rope.
Pulling up IS counted as a rope.
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21. Inclined PlaneA flat slanted surfaceExamples: ramps, stairs, ladder
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An inclined plane does NOT move when work isbeing done.
MA = Length / Height
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22. WedgeA single, double, or multi-sloped inclined planethat MOVES to do work.
Used to split or push objects apart.
Examples: Needle, log splitter, chisel, knife,nail
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23. ScrewAn inclined plane that spirals around a metalrod.
This winding forms grooves and ridges
Threads are the ridges on a screw
Examples: jar lid, Drill bit, car jack
Screws do two functions: Lift heavy objects &
Hold things together.
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24. Compound MachineAny machine that is made up of more than onesimple machine.
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25. FrictionThe rubbing of 2 surfaces together
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26. Friction can be
reduced by:Using smooth surfacesUsing rollers, wheels, or ball bearings
Applying lubricants to surfaces
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27. Examples of useful
frictionStriking a matchSanding wood
Driving with snow tires or chains
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28. EfficiencyComparison of work input to work output.No machine is 100% efficient