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
Inclined Plane
Screw
Pulley
Lever
Wedge
Wheel and Axle
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
 Pulleys
planes
Inclined Planes
 Look
for what you need to fill in as you
watch this video: Inclined Planes
Inclined Planes
–
 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.
 Advantage
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.
Pulleys
 Look
at the questions you need to
answer.
 Pulleys video
Pulley Examples:
Flag pole
Fishing reel
Clothing line
Crane
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
The direction you pull and the
pulley is attached direction of the load are the
to the object being same.
moved.
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)
A combined pulley is a
pulley system made of a
fixed and movable pulley

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
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 machines
 All
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?