Simple Machines
Essential Standard 3.1Understand types of energy,
conservation of energy, and
energy transfer.
Learning Objective 3.1.4
Explain the relationship among work, power,
simple machines both qualitatively and
quantitatively.
I Can StatementsAt the end of this lesson, you should be
able to say, with confidence:
• I can explain how machines make doing
work easier
• I can list six different types of simple
machines.
• I can explain how each of the six different
types of simple machines make doing work
easier
MachineA Machine is a device that makes doing
work easier
W = F x D
Three Ways Machines Make Work Easier
1.Increasing the Force applied to an object
2. Increasing the Distance over which a force can be applied
3. Changing the Direction of an Applied Force
Increasing ForceA Car Jack increases the force applied by increasing
the distance over which the force is applied
You apply a small over a long distance
The car jack applies a large force over a small
distance
Increasing DistanceA ramp allows you to use less force by increasing the
distance over which the force is applied
Changing Direction
An Ax Changes the Direction of the force.
The easier downward force is changed to a sideways
force by the wedge shape of the ax.
ForcesIn order to move something you have to apply enough force to overcome the object’s natural
resistance to being moved.
Resistance Forces are usually Friction,
Inertia, or Gravity.
Input & Output Forces
The Force Applied to the Machine by the person is
called the Input Force.
The Force Applied by the Machine is called the
Output Force
Ideal MachineAs Ideal Machine is One Where the
Amount of Input Work Equals the
Amount of Output Work by the
Machine
But
Some of the Work Put In is
Transferred to Friction and Cannot
Be Used to Do Work
EfficiencyEfficiency is a Measure of Much Work
Put into a Machine is Changed into
Useful Work Put Out by the Machine
Efficiency = Output Work x 100%
Input Work
Grease or Oil can be added to machines to
increase their efficiency
Simple MachinesA Simple Machine Does Work With
Only One Movement of the Machine
Six Types of Simple
Machines
1. Lever
2. Pulley
3. Wheel and Axel
4. Inclined Plane
5. Screw
6. Wedge
LeversA Lever is a Bar That is Free to
Pivot or Turn Around a Fixed Point
The Fixed Point Is
Called the Fulcrum
Fulcrum
First Class LeverA First Class Lever has the Fulcrum
Located Between the Input and
Output Forces
Second Class Lever
A Second Class Lever has the
Output Force Located Between the
Fulcrum and the Input Force
Third Class LeverA Third Class Lever has the Input Force
Applied Between the Fulcrum and the
Output Force
PulleysPulley is a Grooved Wheel with a
Rope, Chain, or Cable Running
Along the Grove
There are Fixed
Pulleys, Movable
Pulleys, and Block
and Tackle Pulleys
Fixed Pulleys
Fixed Pulleys
Change Only the
Direction of the
Force so the Output
Force Equals the
Input Force
Movable PulleysA Movable Pulley is One in Which One
End of the Rope is Fixed and the
Wheel is Free to Move
The Attached Side of the Rope
Supports Half the Weight, So
Force is Increased and You Only
Have to Exert Half the Weight
Block and TackleBlock and Tackle Pulleys Consist of a
System of Fixed and Movable Pulleys
The Weight is Supported Equally
Among Each Supporting Rope
and Force is Increased Allowing
you to Exert Less Weight
Wheel and AxelA Wheel and Axel Consists of an Axel
Attached to the Center of a Larger
Wheel, so that the Wheel and Axel
Rotate Together.
Inclined PlanesInclined Planes have Sloping Surfaces
that Increase the Distance But Reduce
the Force Needed to do Work
ScrewsA Screw is an Inclined Plane
Wrapped in a Spiral Around a
Cylindrical Post
WedgeA Wedge is an Inclined Plane With
One or Two Sloping Sides that
Changes Direction of the Force
Compound MachineCompound Machines Consist of
Two or More Simple Machines that
Operate Together
The End
Top Related