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# 14.4 - PowerPoint PPT Presentation

14.4. Simple Machines. The 6 Simple Machines. Lever Wheel and Axle Inclined Plane Wedge Screw Pulley. Lever. Rigid bar that is free to move around a fixed point Fulcrum = Fixed point a lever rotates around Input Arm = Distance between the fulcrum in a lever and the input force

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## 14.4

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Presentation Transcript

### 14.4

Simple Machines

The 6 Simple Machines
• Lever
• Wheel and Axle
• Inclined Plane
• Wedge
• Screw
• Pulley
Lever
• Rigid bar that is free to move around a fixed point
• Fulcrum = Fixed point a lever rotates around
• Input Arm = Distance between the fulcrum in a lever and the input force
• Output Arm = Distance between the fulcrum in a lever and the output force
IMA of a lever
• IMA = Input Arm / Output Arm
First Class Lever
• The fulcrum is located between the input force and the output force
• Example: Seesaw, scissors
• MA <, >, or = 1
Second Class Lever
• Output force is located between the input force and the fulcrum
• Example: Wheelbarrow
• MA > 1
Third Class Lever
• Input force is located between the fulcrum and the output force
• Examples: Baseball bat, hockey stick
• MA < 1
Wheel and Axle
• Simple machine that consists of two rigidly attached disks or cylinders, each one with a different radius
Wheel and Axle
• IMA = (radius where the input force is exerted) / (radius where the output force is exerted)
• IMA <, or > 1
• IMA for a steering wheel is > 1
Inclined Planes
• Slanted surface along which a force moves an object to a different elevation
• Why do they exist?
• The input force is decreased when the input distance is greater than the output distance
Wedge
• V-shaped object whose sides are two inclined planes sloped toward each other
• Often used to split wood.
Screw
• Inclined plane wrapped around a cylinder
• Screws with threads that are closer together have a greater IMA
Pulley
• Simple machine that consists of a rope that fits into a groove in a wheel
Fixed pulley
• Wheel attached in a fixed location
• Only able to rotate in place
• Direction of the input force is changed, not the size
• IMA = 1
Movable Pulley
• Attached to an object being moved
• Used to reduce the input force needed to lift a heavy object
• IMA = 2
Pulley System
• Combination of fixed and movable pulleys
• IMA of a pulley or pulley systems = number of rope sections supporting the load being lifted
• To move this object

5 m up, I need to

pull 20 m of rope

Compound Machine
• Combination of two or more simple machines that operate together
• The output force of one simple machine becomes the input force for another simple machine