# Chapter 14 Section 3.

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Chapter 14 Section 3

Simple Machines There are 6 basic types of simple machines.
The inclined plane The wedge The screw The lever The wheel and axle The pulley

Inclined Plane Inclined plane is a flat, sloped surface.
It allows you to exert your input force over a longer distance. Mechanical Advantage = Length of incline Height of incline

Wedge A wedge is a device that is thick at one end and tapers to a thin edge at the other end. When you use a wedge, instead of moving an object along the inclined plane, you move the inclined plane itself. Mechanical Advantage=Length of wedge width of wedge

Screws A screw can be thought of as an inclined plane wrapped around a cylinder. The threads of a screw act like an inclined plane to increase the distance over which you exert the input force. The closer together the threads of a screw are, the greater the mechanical advantage. Think of the length around the threads as the length of the inclined plane.

Levers A lever is a rigid bar that is free to pivot, or rotate, on a fixed point (fulcrum). 1. Think about opening a paint can. Pg. 426. 2. Mechanical Advantage = Distance from fulcrum to input force ÷ distance from fulcrum to output force.

Classes of Levers First-Class Levers – always change the direction of the input force. Ex. Scissors, pliers, seesaws.

Second-Class Levers – increase force, but do not change direction of the input force. Ex. Doors, nutcrackers, bottle openers.

Third-Class Levers – increase distance, but do not change the direction of the input force. Ex. Fishing poles, shovels, baseball bats

Wheel and Axle A wheel and axle is made of two circular or cylindrical objects fastened together that rotate about a common axis. The larger radius is the wheel The smaller radius is the axle Ex. Screwdriver, doorknob, steering wheel.

Wheel and Axle How It Works pg. 428

Pulley A pulley is made of a grooved wheel with a rope or cable wrapped around it. 1. decreases the amount of input force needed and changes direction of input force. Ex. flagpoles

Types of Pulleys Fixed Pulley – does not change amount of force. Only changes the direction of force.

Movable Pulley – increases output force. Does not change direction.

Block and Tackle – made up of both a fixed and moveable pulley.
SEE PAGE 431

Compound Machines A machine that utilizes two or more simple machines.