6.3 – Simple Machines

Objectives Describe and identify examples of the six types of simple machines. Explain how the different types of simple machines make work easier.

Simple Machines A machine that does work with only one movement Two Families Levers – levers, pulleys, & wheel and axle Inclined Planes – inclined plane, screw, & wedge

Lever Bar that is free to pivot about a fixed point Fixed point = fulcrum Input arm is part on which input force is applied Output arm is part that exerts the output force

First-class Levers Fulcrum is located between input and output forces Multiplies and changes direction of force http://www.sciencebyjones.com/Firce_class_lever_drawing.gif http://www.cool-science-projects.com/images/man-and-lever.jpg

Second-class Levers Output force is located between input force and fulcrum Always multiplies force http://cache.eb.com/eb/image?id=63039&rendTypeId=4

Third-class Levers Input force is between output force and fulcrum Doesn’t multiply force but does increase distance over which force is applied

3rd class lever Input force- your hand squeezes the stapler Output force- the staple goes through the papers Fulcrum

Classes of Levers First Class Lever Second Class Lever Third Class Lever

Lever & Ideal MA Calculating ideal mechanical advantage (IMA) of a lever: IMA = length of input arm divided by length of output arm

Pulley A grooved wheel with a rope, simple chain, or cable running along a groove Modified first-class lever The point in the middle of the wheel is the fulcrum The rest of a wheel acts like the rigid arm. Three types: fixed, moveable, block &tackle http://www.technologystudent.com/gears1/pulley7.htm

Types of Pulleys Fixed = attached to something and doesn’t move Force is not multiplied but direction is changed IMA = 1

Types of Pulleys Movable = has one end of the rope fixed and the wheel free to move Multiples force IMA = 2

Types of Pulleys Block & Tackle = system of pulleys consisting of fixed and movable pulleys IMA = number of ropes supporting the weight

Block and Tackle Pulley website

Lever and Pulley Video Clip

Wheel & Axle Machine with two wheels of different sizes rotating together Modified lever

Wheel & Axle IMA = radius of wheel divided by radius of axle Gears are modified forms

Inclined Plane Sloping surface that reduces the amount of force required to do work

Inclined Plane IMA = length of slope (input distance) divided by height of slope (output distance) Less force is required if ramp is longer and less steep

Screw Inclined plane wrapped in a spiral around a cylindrical post IMA = Length of Handle divide by length of Shaft

Wedge Inclined plane with one or two sloping sides http://kmoddl.library.cornell.edu/stillImages/Clark/small/003.jpg

Compound Machine Uses a combination of two or more simple machines

Cool Links Simple Machines

In-Class Assignment/Homework 6.3 Reinforcement WKT