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Simple Machines

Levers

Each lever is classified by the location of the loads in relationship to the fulcrum

11stst Class Lever Class Lever

• Fulcrum is located between the effort and the resistance force

• Effort and resistance forces are applied to the lever arm in the same direction

Only class of lever that could have a MA

greater than or less than 1 v

MA =1

Effort Resistance

ResistanceEffort

MA <1

EffortResistance

MA >1

Class 1 Lever

22ndnd Class Lever Class Lever

• Fulcrum is located at one end of the lever

• Resistance force is located between the fulcrum and the effort force

• Resistance force and effort force are in opposing directions

Always has a mechanical advantage >1

Resistance

Effort

Class 2 Lever

33rdrd Class Lever Class Lever

• Fulcrum is located at one end of the lever

• Effort force is located between the fulcrum and the resistance

• Resistance force and effort force are in opposing direction

Always has a mechanical advantage < 1

Resistance

Effort

Class 3 Lever

Wheel & AxleWheel & Axle• A wheel is a lever arm that is fixed to a shaft, which is

called an axle.

• The wheel and axle move together as a simple lever to lift or to move an item by rolling.

• It is important to know within the wheel and axle system which is applying the effort and resistance force – the wheel or the axle.

CalculationsWheel & AxleWheel & Axle

E

R

DIMA =

D

Circumference = 2 π r or π d

Ǿ6 in. Ǿ20 in.

70lb

200lb

Ǿ6 in.

200lb

Ø 20 in.

AMA=E

R

F

F

70lb

Inclined PlaneCalculations

LIMA =

H

4 ft

15 ft

A flat surface set at an angle or incline with no moving parts

Able to lift objects by pushing or pulling the load

Inclined PlaneInclined Plane

Pulley

800 lb

230 lb

800 lb

IMA- Count Strands Pulling down (don’t count) Pulling up (count)

E

R

F

FAMA =

PulleyPulley• A pulley is a lever consisting of a wheel with a

groove in its rim which is used to change the direction and magnitude of a force exerted by a rope or cable.

Functions as a moving inclined plane

Tapers to a thin edge and is used for splitting, raising heavy bodies, or for tightening by being driven into something

WedgeWedge

WedgeCalculations T 3 ft

L

10 ft

LIMA =

T

An inclined plane wrapped around a cylinder, forming the path and pitch

A wheel and axle used to create rotary motion

ScrewScrew

Two Components

Properties

Change rotary motion into linear motion

Used as a threaded fastener

Large MA

Large amount of friction loss

Screw

Diameter

Effort Arm Distance – If using a wrench, effort arm distance would be the length of the wrench

Pitch

Distance between threads and linear distance traveled by 1 rotation of the screw

E2ΠrCircumferenceIMA = =

Pitch P