1. 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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2. Simple Machines
Physical Science
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3. 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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4. 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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5. Lever Lever  Bar that pivots around fixed point.
Fixed point = fulcrum
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6. Three Classes of Levers
IF F OF
1st Class Lever
F OF IF
2nd Class Lever
F IF OF
3rd Class Lever
IF = Input force
F = Fulcrum (pivot point)
OF = Output force
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7. Three Classes of Levers
1st class lever
Change direction of force
Examples: scissors, seesaw
IF F OF
Fulcrum is always between input force and output force in a first-class lever.
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8. Three Classes of Levers
2nd class lever
Does not change direction of force
Examples: wheelbarrow, paper cutter
F OF IF
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9. Three Classes of Levers
3rd class lever
Examples: baseball bat, arm, golf club, tennis racket
F E R
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10. 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
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11. Mechanical Advantage and Levers
Output Arm
Input Arm
Output Arm
Input Arm
Input Arm
Output Arm
IMA > 1
IMA = 1
IMA < 1
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12. Which type of lever?
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13. Which type of lever?
3rd Class Lever
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14. Which type of lever?
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15. Which type of lever?
2rd Class Lever
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16. Which type of lever?
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17. Which type of lever?
1rd Class Lever
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18. Which type of lever?
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19. Which type of lever?
3rd Class Lever
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20. Which type of lever?
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21. Which type of lever?
1rd Class Lever
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22. A Crowbar Is A First-Class Lever
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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23. Pulley Pulley  a chain, belt, or rope wrapped around a wheel…
Can change direction or size of Force.
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24. 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.
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25. 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.
100 lbs
100 lbs
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26. A Moveable Pulley Does not change direction of force. MA = 2
50 lbs
Does not change direction of force.
MA = 2
Allows you to lift a 100-pound weight with only 50 pounds of force, but…
2 feet
1 foot
100 lbs
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27. Pulley
You can combine fixed and movable pulleys to increase the MA even more…
This is a pulley system…
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28. Pulley Systems
IMA = 1
IMApulley = strands of rope that support the mass.
IMA = 4
IMA = 2
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29. Inclined Plane Inclined plane  slanted surface used to raise obj.
A ramp.
IMA of ramp > 1
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30. Inclined Plane
Height
Length of plane
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31. Without An Inclined Plane
Force
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32. With An Inclined Plane (And Rollers)
Force
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33. 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...
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34. Wedges
Compare the force needed to split a piece of wood using each axe head. Which axe head has the higher MA? 10 20 30 40 50 60
Newtons 10 20 30 40 50 60
Newtons
The sharper axe head has the higher Mechanical Advantage. It takes less force to do the same amount of work.
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35. Screw Screw  Inclined plane wrapped around cylinder. Examples:
Closer threads  larger AMA...
Examples:
Hardware screw
Light bulb base
Jar lid
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36. Without Screws
Lifting this gate manually is hard work; it requires lots of force.
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37. With Screws
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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38. 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…
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39. 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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40. Gears A gear is a modified wheel and axle.
Gears can change the size or direction of a force.
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41. 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.
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