Transcript of V205.07 Simple Machines. Devices such as levers, ramps, and pulleys that make our work easier. They...
- Slide 1
- V205.07 Simple Machines
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- Devices such as levers, ramps, and pulleys that make our work
easier. They allow us to apply effort at one place to do work at
another point and/or to change the direction of a force.
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- Simple Machines One way is to magnify an effort force so that a
smaller effort can be applied over a longer distance thus moving a
large load a small distance. Examples: a crowbar being used to
dislodge a boulder, a nutcracker being used to crack a nut, or a
block tackle pulley system being used to lift a large weight.
Source:http://www.lakelandschools.org/EDTECH/Machines/RubeMain.jpg
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- Simple Machines The mechanical advantage of a machine is the
ratio of the load force to the effort force. The crowbar,
nutcracker, and block and tackle pulley system have a mechanical
advantage greater than one. Other machines have a mechanical
advantage less than one allowing magnification of the distance and
speed of a movement. An example of this might be a fishing rod or
baseball bat.
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- Simple Machines Inclined plane -- a sloping surface, such as a
ramp. An inclined plane can be used to alter the effort and
distance involved in doing work, such as lifting loads. The
trade-off is that an object must be moved a longer distance than if
it was lifted straight up, but less force is needed. Examples:
staircase, ramp, and bottom of a bath tub Source:
http://www.sirinet.net/~jgjohnso/inclineplanecolored.jpg
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- Simple Machines Wedge -- two inclined planes joined back to
back. Wedges are used to split things. Examples: Axe Zipper
Knife
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- Simple Machines Screw -- an inclined plane wrapped around a
shaft or cylinder. This inclined plane allows the screw to move
itself or to move an object or material surrounding it when
rotated. Examples: Bolt Spiral staircase wood screw Corkscrew
screws on light bulbs
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- Simple Machines Wheel and axle -- a wheel and axle has a larger
wheel (or wheels) connected by a smaller cylinder (axle) and is
fastened to the wheel so that they turn together. When the axle is
turned, the wheel moves a greater distance than the axle, but less
force is needed to move it. The axle moves a shorter distance, but
it takes greater force to move it. Examples: Door knob Wagon Toy
car Bicycle gears Screw driver
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- Simple Machines Pulley -- a wheel that usually has a groove
around the outside edge. This groove is for a rope or belt to move
around the pulley. Pulling down on the rope can lift an object
attached to the rope. Work is made easier since pulling down is
assisted by gravity. Examples: Flag pole Crane Elevators Window
blinds Source:
http://www.edinformatics.com/math_science/simple_machines/pulley.htm
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- Simple Machines Lever -- a straight rod or board that pivots on
a point known as a fulcrum. The fulcrum can be moved depending on
the weight of the object to be lifted or the force you wish to
exert. Pushing down on one end of a lever results in the upward
motion of the opposite end of the fulcrum. Examples: Door on hinges
Seesaw Hammer Bottle opener
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- Classes of Levers The class of a lever is based on the relative
position of the load, effort, and fulcrum. Levers are classified
into 1st class, 2nd class and 3rd class levers.
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- Classes of Levers 1st class: Crowbar Scissors
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- Classes of Levers 2nd class: Nutcracker Wheelbarrow Doors
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- Classes of Levers 3rd class: Tennis racket Tweezers
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- Questions about Simple Machines What is a simple machine? What
are the 6 simple machines? How does each simple machine work? How
does each machine make work easier? What are the classes of levers
and how do they work? What is mechanical advantage?