Simple Machines

TEKS

6.8E – investigate how inclined planes and pulleys can be used to

change the amount of force to move and object

7.7A – contrast situations where work is done with different amounts

of force to situations where no work is done such as moving a box

with a ramp and without a ramp, or standing still

What are simple machines?

The 6 Simple Machines

Lever

PulleyWheel and Axle

WedgeScrewInclined Plane

Why use a SIMPLE machine??

SIMPLE Machines help us in 2 ways:

1. Change the amount (magnitude) of

force on an object.

2. Change the direction of the force.

3. A simple machine has few or no

moving parts and use only the force

(effort) of a person to do the work.

4. They also give us something called

mechanical advantage.

We will focus on:

Inclined planes

Pulleys

Inclined Planes

Look for what you need to fill in as you

watch this video: Inclined Planes

Inclined Planes

Advantage –

An inclined plane is a slanted surface

that makes it easier to move objects

up and down.

You can use an inclined plane to help

move an object to a higher place or a

lower place.

Disadvantage is that you have to move it

a farther distance.

Inclined Planes

Every day Examples: Ramp, stairs, slides

How did Egyptians build such

large pyramids?

Inclined Plane The Egyptians used simple machines to build the

pyramids. One method was to build a very long

incline out of dirt that rose upward to the top of the

pyramid very gently. The blocks of stone were

placed on large logs (another type of simple machine

- the wheel and axle) and pushed slowly up the long,

gentle inclined plane to the top of the pyramid.

PulleysLook at the questions you need to

answer.

Pulleys video

Pulley Examples:

Flag pole Crane

Fishing reel

Clothing line

Pulley vocabulary

Pulley system – a group of two or more

pulleys that work together to lift a load.

Mechanical advantage - how much a

machine multiplies the effort force put

into it.

Types of pulleys – fixed, movable and

combined pulleys. Combined pulleys are

also called “block and tackle” pulleys.

Types of pulleys – Fixed (1)

A fixed pulley is

attached to

something that

does not move.

The wheel of the pulley turns and

lifts the load and changes the

direction of the force.

The effort needed to lift this load

is equal to the weight of the load.

You must also pull a length of rope

equal to the distance you wish to

lift the load.

Types of Pulleys – Movable (2)The wheel of the

pulley is attached

to the object being

moved.

The direction you pull and the

direction of the load are the

same.

The effort needed to lift this

load is ½ the weight.

This pulley system provides

Mechanical Advantage.

However, the rope must be

pulled twice the distance that

the load is moved.

Type of pulleys – Combined (3)

These pulleys

change the direction

of the force and

increase the force.

The more pulleys,

the less amount of

force or effort you

need to apply.

Provide a

mechanical

advantage

A combined pulley is a

pulley system made of a

fixed and movable pulley

Combining fixed and moveable pulleys makes a

Compound Pulley System. This allows the user to gain

both Mechanical (less effort to lift) and Directional

Advantage.

The more rope arms supporting the load the greater the

Mechanical Advantage, so less force or effort is needed

to lift the load.

Exploring Mechanical Advantage:

Mechanical advantage =

the distance over which one must apply

the force

the distance one wishes to move an

object

MA and Simple machinesAll pulleys have a fixed MA depending

on the type.

single fixed pulley has an MA = 1.

single moveable pulley has a MA = 2.

A pulley with 4 ropes (block and tackle

or combined) has an MA = 4.

An inclined plane also has a mechanical

advantage: MA = length

height

Comprehension check!

Do simple machines make work easier?

This is a trick question! Machines don't increase or

decrease the amount of work done, but they do make the

(YOUR) work easier!

How do they accomplish this?

Remember, the amount work done is the same with or

without the use of a machine.

When we use a machine, however, we change either the

amount of force needed or the distance over which the

force acts.

Think it through:

Is the same amount of work being

done?