Bell ringer If the input force is bigger than the output force, then the input distance is...
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Transcript of Bell ringer If the input force is bigger than the output force, then the input distance is...
Bell ringer If the input force is bigger than the output force, then the
input distance is __________ than the output distance.
If the output force is bigger than the input force, then the input distance is __________ than the output distance.
If the input force is smaller than the output force, then the input distance is __________ than the output distance.
If the output distance is bigger than the input distance, then the input force is __________ than the output force.
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Types of Machines:
Simple machines are simple tools used to make work easier.
Compound machines have two or more simple machines working together to make work easier.
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Simple Machines Simple Machine Does work with one
movement... There are six simple machines:
(1) lever (2) pulley (3) inclined plane (4) wedge (5) screw (6) wheel and axle
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Three Classes of Levers
IF F OF
1st Class Lever
F OF IF
2nd Class Lever
F IF OF
3rd Class Lever
IF = Input forceF = Fulcrum (pivot point)OF = Output force
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Three Classes of Levers 1st class lever
Change direction of force Examples: scissors, seesaw
Fulcrum is always between input force and output force in a first-class lever.
IF F OF
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Three Classes of Levers 2nd class lever
Does not change direction of force Examples: wheelbarrow, paper cutter
F OF IF
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Three Classes of Levers 3rd class lever
Examples: baseball bat, arm, golf club, tennis racket
F E R
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Mechanical Advantage and Levers 2 arms of lever:
The input arm is the distance between the input force and the fulcrum.
The output arm is the distance between the output force and the fulcrum.
If input arm > output arm, IMA > 1 If input arm = output arm, IMA = 1 If input arm < output arm, IMA < 1
Output ArmInput Arm
Mechanical Advantage and Levers
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Output Arm
Input Arm
Input Arm
Output Arm
IMA = 1
IMA < 1
IMA > 1
A Crowbar Is A First-Class Lever
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A crowbar is a first-class lever. It changes the direction of the applied force. Because it has a long effort arm and a short resistance arm, it also greatly multiplies the force.
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Pulley
Pulley a chain, belt, or rope wrapped around a wheel… Can change direction or size of Force.
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Pulley Fixed pulley one that is attached to a
ceiling, wall, etc. Only changes the direction of the effort force MA of a single fixed pulley is always one.
Movable pulley pulley hung on a rope that it moves with the effort force… Can multiply the effort force, but cannot
change the direction… MA for movable pulley is always greater than
one.
A Fixed Pulley Changes
direction of force.
MA = 1 Use just as
much force to lift the box as you would by picking it up directly.
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100 lbs
100 lbs
A Moveable Pulley Does not change
direction of force.
MA = 2
Allows you to lift a 100-pound weight with only 50 pounds of force, but…
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100 lbs
50 lb
s
2 feet
1 foot
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Pulley
You can combine fixed and movable pulleys to increase the MA even more…
This is a pulley system…
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Wedge Wedge a V-shaped object whose
sides are two inclined planes sloped toward each other.
Examples include: knife blade razor blade axe head a door stopper
Sharpening increases AMA...
Wedges
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010
20
3040
50
60
Newtons
010
20
3040
50
60
Newtons
Compare the force needed to split a piece of wood using each axe head. Which axe head has the higher MA?
The sharper axe head has the higher Mechanical Advantage.
It takes less force to do the same amount of work.
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Screw Screw Inclined plane
wrapped around cylinder. Closer threads larger AMA...
Examples: Hardware screw Light bulb base Jar lid
With Screws
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Screws change rotational motion into straight-line motion. It takes a lot less force to lift the gate, but it takes a longer time.
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Wheel and Axle Wheel and axle a lever that rotates
in a circle… Made of two wheels of different sizes… Axle is a smaller wheel… Larger wheel turns about the smaller axle… Wheel moves through a greater distance; Effort force applied to the wheel is multiplied at
the axle… Examples:
Bicycles, Ferris wheels, water wheels, gears…
Wheel and Axle The wheel and axle
makes it easier to raise the crate.
Any force applied to the large wheel is multiplied in the smaller axle.
But the wheel must be turned much farther to lift the crate.
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Gears A gear is a
modified wheel and axle.
Gears can change the size or direction of a force.
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Compound Machines Compound machines
combination of two or more simple machines…
***Remember…simple or compound, you can get no more work out of a machine than you put into it!! Machines cannot multiply work!!!
An automobile engine is a compound machine made of many simple machines, including pulleys, wheels and axles, levers, and screws.