Machines and Mechanical Advantage

   Archimedes (Greek mathematician, 287 to 212 B.C.) said, “Give me a place to stand and I will move the Earth,” meaning that if he had a lever long enough, he could move the Earth by

his own effort

Mechanical Advantage (M.A.)

• the number of times a machine multiplies the effort force (FE ) put into it

• the more times the machine multiplies the effort force, the easier the job

M.A. = Mechanical AdvantageFR = Resistance Force or LoadFE = Effort ForceDE = Effort DistanceDR = Resistance Distance

M.A.= FR DE

FE DR

Mechanical Advantage formula

or

Example problem using forces

• What is the mechanical advantage of a machine where an effort force of 20 N will lift a load of 180 N?

FR = 180N MA = FR 180N/20N 9FE = 20N FE

given formula set up problem answer w/ unit of measurement

There is no unit of measurement on mechanical advantage

Example problem using distances

• What is the mechanical advantage of a machine where an effort distance of 20 meters will lift a load of 5 meters high?

DR = 5m MA = DE 20m/5m 4DE = 20m DR

given formula set up problem answer w/ unit of measurement

There is no unit of measurement on mechanical advantage

Six Types of Simple Machines

• basically a ramp

• has no moving parts

• decreases the effort force needed to move an object but increases the distance necessary to move it

1. Inclined Plane

The Inclined Plane Family

http://kosmoi.com/Science/Physics/Machines/Incline/

Wedge• an incline plane that moves through

something

• normally made up of two inclined planes

Screw• an inclined plane that is wrapped around to

form a spiral

• multiplies the effort force by increasing the distance

Lever• a rigid bar that is free to pivot on a fulcrum

• Three classes of levers

–First Class

The Lever Family

–Second class

– Third class• the only lever that

does not multiply the effort force• but is does increase

speed and distance of what you are moving

Pulley

• a rope, belt, chain… wrapped around a grooved wheel

• changes the direction of the force

• may multiply the effort force to lift heavy loads when using many pulleys

Wheel and Axle• a lever or pulley connected to a shaft– the wheel is the larger circle/lever/pulley– the axle is the smaller circle/shaft/axle

Compound Machines

• a combination of two or more simple machines