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