Energy, Work, & Machines

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

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Energy, Work, & Machines