Simple MachinesSimple Machines

Friction ReviewFriction Review

Friction is the Friction is the forceforce we feel when things we feel when things rubrub against each otheragainst each other

The The moremore things things are pushedare pushed together, the together, the moremore friction there is friction there is

It is the force that It is the force that opposesopposes motion. motion.

Friction ReviewFriction ReviewFriction Friction slowsslows down down the movement ofthe movement of things things

and turns motion into and turns motion into thermal energy thermal energy (heat).(heat).

When you When you rub your hands togetherrub your hands together you can you can feel the thermal energy produced.feel the thermal energy produced.

The mucus from The mucus from aa slugslug will will decreasedecrease friction friction as the slug slides along the ground.as the slug slides along the ground.

Simple MachinesSimple Machines

The purpose of a simple machine is to

A. increase the speed of work

B. change direction the force is acting in

C. increase Mechanical Advantage

- a machine’s ability to multiply input force

Inclined Inclined PlanePlane

A flat surface placed at an angle to a horizontal surface:

Examples:Examples:

Ramp, roadways, slide, Ramp, roadways, slide, stairsstairs

LeverLever

A lever is a rigid bar that rocks back and forth at the fulcrum

When a force is applied at one end, the other end moves.

The object to be moved is the load

Types of LeversTypes of LeversThere are three types of levers:

1st class lever- fulcrum is between the force and the load: crowbar, seesaw, pliers

2nd class lever – load is between the force and the fulcrum: nutcracker

3rd class lever – load and fulcrum are at either end: broom, baseball bat, hammer

WedgeWedge

A wedge is made of 2 inclined planes put together

A force is applied to the wedge to drive it into an object

Examples:knife, chisel, nail, axe

PulleyPulleyA pulley is a wheel with a grooved rim for

placement of a rope.

A downward force on one side

results in an upward movement

on the other side.

Examples:

flagpole, curtain cord, mini-blinds

Two Types Two Types of Pulleysof Pulleys

1. a fixed pulley –

attached to an object

2. a moveable pulley –

moves with the object

ScrewScrew

A screw is a spiral inclined plane.

Examples:

jar lid, machine screw, mountain road

Wheel and AxleWheel and Axle

A bunch ofA bunch of levers levers pivoting around one pivoting around one fulcrum.fulcrum.

A wheel or crank A wheel or crank

attached to an attached to an axleaxle. .

Examples:Examples:

door knob, wheels of vehicles, gearsdoor knob, wheels of vehicles, gears

Compound (Complex) MachinesCompound (Complex) Machines

A complex machine is made of two or more simple machines.

Examples:Bicycle, wheel barrow, Rube Goldberg machine

List the simple machines in the Rube Goldberg complex machine that are numbered.