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Simple Machines 1 Effort Efficiency Mechanical Advantage WORK Force
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Goals Be able to calculate mechanical advantage
2 Goals Analyze the simple machines qualitatively and quantitatively in terms of force, distance, work and mechanical advantage Be able to calculate mechanical advantage Be able to calculate amount of work done by a simple machine Explain the different types of simple machines.
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Work FLASH BACK Transfer of Energy from one place to another.
3 Work FLASH BACK Transfer of Energy from one place to another. Applying a force over a certain distance. Calculating Work: Work (J)= Force x distance W = f x d Power= work/time
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6 types of simple machines
4 6 types of simple machines clip
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What is a machine? A device that makes work easier.
5 A device that makes work easier. What is a simple machine? -a machine that does work with only one movement. You still do the same amt of work —it’s just easier!
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A machine can make work easier in two ways:
6 A machine can make work easier in two ways: Multiply the force you apply. A Car Jack Change the direction of the force. Blinds
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7 Mechanical Advantage CLIP Number of times the machine multiplies the effort force (The force you apply to it)
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Watch for this in all Simple machines:
8 Watch for this in all Simple machines: Machines are a “give and take relationship.” If you get your force multiplied, then you must go a greater distance.
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Efficiency of a Machine
9 A measure (%) of how much work put into a machine is actually changed to useful work put out by the machine. 90 J . 100 J NEVER OVER 100%
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According To “The Law of Conservation of Energy” Can this exist?
10 Ideal machine Efficiency =100% MA= 100% According To “The Law of Conservation of Energy” Can this exist? Does not exist. FRICTION
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Types of Machines Levers
11 Types of Machines Levers A lever is a bar that is free to pivot, or turn about a fixed point. How can we use levers?
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Levers 12 Fulcrum Resistance Distance Effort Distance LOAD Effort Arm
Resistance Arm Resistance Force Effort Force
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Levers There are three types of Levers
13 Levers There are three types of Levers Based on the position of the fulcrum
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The fulcrum is between the resistance force and the effort force.
14 Levers 1st Class: Crowbars, pliers, scissors, seesaw The fulcrum is between the resistance force and the effort force. The closer the fulcrum to the resistance force, the more the lever multiplies the force.
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Levers 15 Wheelbarrow Nutcrackers Crowbar (forcing two objects apart)
2nd Class: The resistance force is between the effort force and the fulcrum. Wheelbarrow Nutcrackers Crowbar (forcing two objects apart) The handle of a pair of nail clippers
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16 3rd Class: the effort force is between the resistance force and the fulcrum. Levers Hoe Your arm Catapult Fishing rod Tongs (double lever) (where hinged at one end)
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Mechanical Advantage of Levers
17 5/5=1 10/5=2 20/5=4 Effort arm Resistance arm As the length of the effort arm increases, the MA of the lever increases.
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18 REVIEW Position of Fulcrum
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19 Pulleys
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Pulleys Multiply the effort force change the direction of the force 20
What is a pulley? A pulley is a grooved wheel with a rope or chain running along the groove. What can a pulley be used for? Multiply the effort force change the direction of the force
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Pulleys 21 Two types of Pulleys: Fixed pulley Movable pulley
A pulley that is attached to something Only changes the direction of the force Movable pulley The pulley is free to move ***Block and Tackle*** Combination of both types of pulleys
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Mechanical Advantage of Pulleys
22 Only changes the direction of the force MA =1 10 N resistance Force Effort Force 10 N
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Mechanical Advantage of Pulleys
23 MA =2
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Mechanical Advantage of Pulleys
24 MA =2
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Mechanical Advantage of Pulleys
25 MA =4
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28 Inclined Plane Resistance Distance (h) Effort Distance (l)
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Mechanical Advantage of Inclined Planes
29 Effort Distance (l) Resistance Distance (h)
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Mechanical Advantage of Inclined Planes
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31 Wheel and Axle Consisting of two wheels of different sizes that rotate together The effort force is applied to the larger wheel
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Ideal Mechanical Advantage = Radius of wheel
Of wheel and axel Radius of axel Gears are wheels with teeth.
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Screw An inclined plane wrapped around a cylinder
32 Screw An inclined plane wrapped around a cylinder The inclined plane lets the screw slide into the wood. Examples: Bolt, Spiral Staircase
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Wedge 34 An inclined plane with one or two sloping sides.
Changes the direction of the effort force. Examples: Axe, Zipper, Knife Effort Force Resistance force
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Review Clip 35
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36 Rube Goldburg
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37 CLIP
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EOCT QUESTIONS 38
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A lever is used to lift a box. The mechanical advantage of the lever is
39 It took only 200 N of force to lift a 1000N object, therefore the machine multiplied the force 5 times! A 25 B 10 C 5 D 4 OR 50 cm 10 cm
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40 What is the amount of useful work output of a 25% efficient bicycle if the amount of work input is 88 N-m? A 2200 N-m B 113 N-m C 63 N-m D 22 N-m Wout .25 = 88 J
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Which of the following is an example of
41 Which of the following is an example of a compound machine? A bicycle B crowbar C doorknob D ramp
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Simple Machines
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