Download Simple Machines PPT

Today’s Objectives
 Understand what a simple machine is and how it
can be used.
 Learn about a Rube Goldberg Machine.
Understand how to construct one using simple
machines.
What is a simple machine?
A machine should assist you in doing work
however, the amount of work done overall
is the same
The most basic objects that redirect force
are called simple machines
Example of a Simple Machine
Remember: Work = Force x Distance
What is a Complex Machine?
More than 1 simple machine to redirect
the work is known as a complex machine.
Also known as a compound machine.
Examples of complex machines:
Scissors, which use two first class levers
joined at a common fulcrum
A car jack, which uses a lever in
combination with a large screw
Why Use Simple Machines?
Since…
Work = Force x Distance
AND overall Work of the system stays constant…
If you increase the force, you decrease the distance
covered
OR
If you increase the distance, you decrease the force
input by the user
Become an Expert:
Inclined Plane
What are we learning about?
What is an inclined plane?
Inclined Planes multiply
and redirect force
An inclined plane turns a
small input force in to a
large output force by
spreading the work out
over more distance
The Inclined Plane Family
A screw is an inclined plane wrapped
around a cylinder
Screws require less force
to insert than nails, but
you cover more distance
because you have to
twist it so many times
The Inclined Plane Family
 A wedge is a modified incline
plane
Used to change direction of a
force
Allows you to apply a force
down onto the wedge and
redirects to force to the sides
Ex: an ax splitting wood
 Note: cheese is not really an example of an
inclined plane, unless you use it as a ramp
Become an Expert:
Pulley
What are we learning about?
Pulleys
The point of rotation
on a pulley is the
fulcrum and the
arm will bend
around the fulcrum.
Fixed Pulleys
 In a fixed pulley the
fulcrum is attached to a
base or structure.
 The input force direction
is opposite the output
force direction.
 Since you input a
downward force on
the rope, the output
force causes the
bucket to move up.
Non-Fixed Pulleys
o Non-fixed pulleys
have the fulcrum NOT
attached to a base or
structure.
o The input force and
output force are in
relatively the same
direction.
Pulleys
Multiple pulleys are
sometimes put
together in a single
unit called a block
and tackle
“Real Life” Examples
Become an Expert:
Lever
What are we learning about?
The Lever Family
 Levers have a rigid arm and a fulcrum
 Rigid Arm: the body of the lever where the output and input
are applied
 Fulcrum: the pivot about which a lever turns
 Levers are divided into three classes
Arm
Fulcrum
First-Class Levers
 All first-class levers have a fulcrum located
between the points of application of the input and
the output forces
 Fulcrum is not necessarily visible or in the exact
center
 Example: a teeter-totter (see-saw)
Input
Force
Arm
Output
Force
Fulcrum
Second-Class Levers
 In a second-class lever, the fulcrum is at one
end of the arm and input force is applied to the
other end, with the output in between
 Example: A wheel barrow
Output
Force
Arm
Input
Force
Fulcrum
Third-Class Levers
 In third-class levers, the input force is
between the output force and the fulcrum
 Example: Fishing Rod
Output
Force
Arm
Input
Force
Fulcrum
Examples of Levers
1st class
Note: You will not
need to be able
to differentiate
between the 3
classes.
2nd class
1st class
3rd class
3rd class
1st class
2nd class
2nd class