# Simple and Complex Machines notes

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Simple and Complex Machines (SC Standards 6-5.7 and 6-5.8) Crossroads Middle School

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Effort A lever is a rigid bar that can pivot on a point to move or lift a load. The point that a lever pivots on is called the fulcrum . The fulcrum can be placed at many different places along the bar. There are two ways levers can reduce the effort force needed to do work: moving the effort force away from the fulcrum moving the load closer to the fulcrum fulcrum lever Object Effort Object Levers

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Types of Levers: First Class Levers Some levers have the fulcrum in the middle: fulcrum effort force load scissors crowbar fulcrum effort force load

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Types of Levers: Third Class Levers Some levers have the effort force in the middle: fulcrum effort force load tweezers broom fulcrum effort force load

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Types of Levers: Second Class Levers Some levers have the load in the middle: fulcrum effort force load wheelbarrow bottle opener fulcrum effort force load

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A pulley has a grooved wheel with a rope running along the groove. Pulleys can change the amount and/or the direction of the effort force. A moveable pulley is attached to the load and moves with it. A moveable pulley reduces the effort force. A fixed pulley is attached to a structure and does not move. It only changes the direction of the force (you pull down and the weight goes up.) Pulleys: Moveable and Fixed

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Examples of Fixed Pulleys the top of a flagpole window blinds

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Examples of Moveable Pulleys construction cranes part of block and tackle systems

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An inclined plane is a sloped surface, like a ramp , that reduces the amount of force needed to lift an object. An inclined plane can reduce the force needed to lift a load in two ways: increase the length of the ramp decrease the height of the ramp Inclined Plane He sure could have used a ramp

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Inclined Plane Examples ramps stairs screws wedges

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A wedge is one inclined plane, or two back-to-back, that can move . Examples of wedges: Inclined Planes that Move knife blades axes teeth nails

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A screw is an inclined plane wound around a post or cylinder . Examples of screws: bolts and jar lids . Inclined Planes Wrapped Around a Post

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Wheel and axles has two circular parts: a central shaft, called an axle , inserted through the middle of a wheel . Examples: door knobs , steering wheels, screwdrivers , gears, and bicycles wheels. Wheel and Axle

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Complex machines, also called compound machines, consist of two or more simple machines in them. Examples may include: scissors consisting of two levers and two wedges a fishing pole has a lever (the pole), a pulley (line), wheel and axle (reel) and a wedge (hook) a bicycle has wheel and axles (gears, wheels, and pedals), levers (handlebars and handbrakes), and a number of screws. Complex Machines