Simple MachinesSimple Machines

• The amount of work you do depends on a force being used to move an object a certain distance. The faster you accomplish it, the more power there is!

Work and Power

So, if someone has to get themselvesup a certain distance, then they have to

do the equivalent amount of work

The height of this staircase is the distance

The effort Homer needs to jump up is the force!

The force of the jumpforce of the jump x height of the stairsheight of the stairs is the work homer accomplished!

It doesn’t matter how fast you do it, as long as the force andthe distance remain the same, the work is the same as well!

How does it apply to real life?

?

If someone needed to lift a box to the top of the pile…

There are two ways to do it but the amount of work is still the same!

They can just pick it up themselves and lift it; but this could take lots of effort!

Or, they could use a machine of some kind that will do the same work but with less

effort!

What is a machine?

• A machine is a device that usually makes work easier

• Main Concept 3: Simple Machines makes work easier by changing two factors: Force & Distance.– Remember: Work = Force x Distance

Distance

Force

You will be seeing how each simple machine manipulates

force and distance.

6 Different Types of Machines Homer could choose from:

Wheel & Axle

Input and Output

Input Force (Effort Side)

• Push or pull that you have to do to the

machine

• Example: Pushing keys on a keyboard

• Person moves a shovel

• Look for green to show the input in this slide

show

Output Force (Result Side)

•Push or pull the machine does on the object

•Example: What appears on a computer screen

•Shovel moves the dirt

•Look for yellow to show the output in this

slide show

Machines involve two forces to accomplish work. Main Concept 4: As a result of the Input force, an Output force occurs

and work gets done on an object!

Input work (Effort Side) Output work (Result Side)

Lever

Fo

rce

Fo

rce

Basically, this is a board that is placed on a pivot point called a fulcrum

As you apply a force to one side the other side applies a force to the

object you want moved!

Here is the distance needed

Inpu

t Wor

k (E

ffor

t Sid

e)

Pulleys

Ou

tpu

t (w

ork

sid

e)

A pulley is a wheel with a rope wrapped around it and attached to the object

you want to move.

When you apply a pull force to one side of the rope, the rope applies a pull

force to the object side and the object gets lifted

Force

Fo

rce Think: has the distance

required changed?

Which side of the pulley is the input and which is the output?

Input work (E

ffort S

ide)

Ou

tpu

t wo

rk (Resu

lt Sid

e)

Incline Plane

Homer may have to push the box up, but it takes less effort than simply lifting it

An incline plane is a ramp that increases the distance needed tomove an object but makes the work easier to do.

Think: has the distance required changed?

Where is the input and output sides?

The work has been spread out over a greater distance than lifting straight up!Therefore it is easier to accomplish (takes less effort)!

Wedge:

Output Force

Inp

ut F

orce

A wedge works like two A wedge works like two ramps put together. ramps put together.

As the input force pushes down, As the input force pushes down, the output force pushes out, the output force pushes out,

splitting the object splitting the object

The Wheel & Axle

Either the axel turns the wheel or the wheel turns the axel.

The input and output of a wheel The input and output of a wheel and axel and axel

will all depend on how you use it.will all depend on how you use it.

If it is used as a wheel to move a car (or something like it)

Then the input comes through the axel and the output is from the turning

of the wheel

If it is used as steering wheel to

turn (or something like it)

Then the Input comes through the

wheel and the output is from

the axel

Q: How could Homer use a wheel and axle to lift his box?

Homer turns the crank on the wheel and the box on the ramp moves up

Don’t forget!This is the work Homer

Is trying to do!= Lift the box this distance

Now you would have to ask when a machine this size would be worth the effort to make it

Maybe if there were a lot of boxes to lift = more work to do

Compound Machine

Slow Fast

The use of a wheel and axle are actually very common

The rear wheel turns more for each time you pedal causing you to travel farther with less force

“Compound Machine”Any combination of several simple

machines…A compound machine is simply two or more simple machines put A compound machine is simply two or more simple machines put

together.together.

Notice that there are at least 4 different simple machines in this one compound machine

Simple machines are most often usedin combinations like this!