Have few or no moving parts

Make work easierCan be combined to create complex machines

Six simple machines: Lever, Inclined Plane, Wheel and Axle, Screw, Wedge, Pulley

We know that a machine multiplies whatever force you put into it:

- Using a screwdriver to turn a screw - Twisting a nail with pliers - Carrying a box up a ramp instead

of stairs**The ratio of the output force (acting on a load ) produced by a machine to the applied effort (the input force).

Abbreviated MA

(IMA) Ideal MA: This is the MA of a machine in a world with no friction, and no force is lost anywhere

(AMA) Actual MA: This is simply the MA of a machine in the world as we know it

- Force is lost due to friction - Force is lost due to wind, etc.

Can we have an ideal machine?

A rigid board or rod combined with a fulcrum and effort

By varying position of load and fulcrum, load can be lifted or moved with less force

Trade off: must move lever large distance to move load small distance

There are 3 types of levers

The mechanical advantage of a lever is the distance from the effort to the fulcrum divided by the distance from the fulcrum to the load

For our example, MA = 10/5 = 2

MA =Distance, effort - fulcrumDistance, load - fulcrum

• Distance from effort to fulcrum: 10 feet

• Distance from load to fulcrum: 5 feet

A slope or ramp that goes from a lower to higher level

Makes work easier by taking less force to lift something a certain distance

Trade off: the distance the load must be moved would be greater than simply lifting it straight up

The mechanical advantage of an inclined plane is the length of the slope divided by the height of the plane, if effort is applied parallel to the slope

So for our plane MA = 15 feet/3 feet = 5

MA =Length of SlopeHeight of Plane

• Let’s say S = 15 feet, H = 3 feet

A larger circular wheel affixed to a smaller rigid rod at its center

Used to translate force across horizontal distances (wheels on a wagon) or to make rotations easier (a doorknob)

Trade off: the wheel must be rotated through a greater distance than the axle

The mechanical advantage of a wheel and axle system is the radius of the wheel divided by the radius of the axle

So for our wheel and axle MA = 10”/2” = 5

MA =Radius of WheelRadius of Axle

2"

10"

An inclined plane wrapped around a rod or cylinder

Used to lift materials or bind things together

The Mechanical advantage of a screw is the circumference of the screwdriver divided by the pitch of the screw

The pitch of the screw is the number of threads per inch

So for our screwdriver

MA = 3.14”/0.1” = 31.4

MA = Circumference of ScrewdriverPitch of Screw

Diam.=1"

10 threadsper inch

Circumference = ∏ x 1” = 3.14”

Pitch = 1/10” = 0.1”

An inclined plane on its side

Used to cut or force material apart

Often used to split lumber, hold cars in place, or hold materials together (nails)

NSF North Mississippi GK8

Much like the inclined plane, the mechanical advantage of a wedge is the length of the slope divided by the width of the widest end

So for our wedge, MA = 6”/2” = 3They are one of the least efficient simple machines

MA = Length of SlopeThickness of Widest End

2"

6"

A rope or chain free to turn around a suspended wheel

By pulling down on the rope, a load can be lifted with less force

Trade off: no real trade off here; the secret is that the pulley lets you work with gravity so you add the force of your own weight to the rope

The Mechanical Advantage of a pulley is equal to the number of ropes supporting the pulley

So for the pulley system shown there are 3 ropes supporting the bottom pulley

MA = 3This means that if you pull with a force of 20 pounds you will lift an object weighing 60 pounds