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 1 IMA for a steering wheel is > 1

Inclined Planes Slanted surface along which a force moves an object to a different elevation

Switchback Roads..\..\switchbackroads.jpg 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