Simple and Compound
Machines
What are Machines?
• Write down a few examples of machines.
– What do you think of when you hear the word
machine?
– How many examples of machines can you
come up with?
– What do we use machines for?
A machine is a device that allows
people to do work with less effort.
• There are two types of machines we will
discuss:
– Simple Machines
– Complex Machines
• Both are mechanical machines, or
machines that do work.
What are Simple Machines?
• A device that allows people to do
work with less effort that has few to
no moving parts.
- They can help us move things closer or apart, raise or
lower to a different height, or change direction of force
What is a force?
• Energy used in a specific direction.
• Ex. Walking forward, pushing a box, sharpening a pencil
The 6 Simple Machines
Lever
A rigid bar used to turn about a fixed point
called a fulcrum.
How does it help us?
It changes the size and
direction of a force.
4 Things You Need To Make A
Lever
Lever Arm - the bar
Fulcrum -the turning point
-Effort force is exerted on one arm (push or pull)
- Load is the opposing weight
Lever Arm
Effort
Load
Fulcrum
We can arrange a lever three
different ways
Do not know how to tell the difference between them? Look at what is in
the middle!
First Class Levers
The typical “see saw” style.
Changes direction of force (push down, resistance goes up)
Examples:
Second Class Lever
Fulcrum is located next to the resistance.
Reduces the force needed to accomplish work.
Examples:
Third Class Lever
Effort located in the middle.
Requires a lot of effort, but makes up by allowing the
resistance to travel a long distance.
Example:
Wheel & Axle
The wheel and axle is a first class lever.
• The fulcrum is replaced with an axle (a rod)
• Lever arms are repeated around the axle.
Rotates the full 360 degrees rather than
“teeter totter”
How does it make work easier?
It can either:
• Reduce the amount of force needed to move a distance
Or
• Increase the distance the object moves (requires more
force)
Depending on where the effort is located: the axle or the
wheel.
Examples:
Pulleys
A grooved wheel that
rotates a rope, belt, or
chain securely around it.
It makes work easier by:
• changing the
direction of force
• Reducing the effort
applied.
Examples of Pulleys
Video
Today
Take out notes/ writing utensil from yesterday
Finish the last 3 simple machines
• Inclined Plane
• Screw
• Wedge
• Compound Machine
• Mechanical Advantage
Worksheet
Inclined Plane
“ At an angle”
“flat surface”
An inclined plane is any slanted surface used to raise a
load from a lower level to a higher level.
How does it make work easier?
Allows heavy objects to be lifted with less effort
(trade off: it moves a longer distance)
Examples of Inclined Planes
Not a simple
machine (the
mountain)
Screw
An inclined plane wrapped
around a cylinder, forming
threads (a path and pitch)
Screws turn rotary motion
into linear motion
Examples of Screws
A screw can either:
•
raise/move weight
•
Press/ fasten
objects together
Wedge
A Wedge is a moving inclined plane
Tapers to a thin edge and is used for:
-Splitting things (pushing them apart)
-Tighten or hold things
-Help grip things (space for fingers)
Examples of Wedges
All cutting tools
make use of the
wedge.
Compound Machines
• Compound machines consist of two or
more simple machines put together.
• Most devices are compound machines.
• They can do more difficult jobs because
their mechanical advantage is greater.
What two simple machines are
in scissors?
First Class Lever and Wedge
Mechanical Advantage
Take these two hills shown:
• You are required to run up and down them 20 times as
fast as you can (they are both the same length). Which
one would you rather run up?
• Why?
Mechanical Advantage
• Is a ratio that expresses how much work
you are actually saving
MA=
Existing weight
acting force or distance traveled
• Simply put, the higher mechanical
advantage, the less you have to do
• Grab your simple machine
worksheet from bin and put in
binder.
• Begin class with 2 minute
discussion
• Does anyone have (and can
bring in) the board game
“Mouse Trap”?