Simple Machines

Definition:

A device that changes the direction of the Force that is applied to do a job.

For Example:

Ramp

In order to lift a crate straight up, you would use a ramp – right?

You want to lift a vertical height

The ramp changes the vertical lift to a diagonal

It takes less force to push an object at an angle to gravity than it is to pick it up in line with gravity.

Ramp

20N

40N

But, since it is a longer distance, you are doing more work with less effort.

So, it doesn't seem as hard of work using the ramp

Ramp Distance

Ver

tical

Dis

tanc

e

Simple machines are Separated into two Families:

1. Lever Family

2. Incline plane Family

Lets start with the levers . . .

TheLever Family

Terminology first - - Fulcrum – The point at which the lever pivots.- Input force – The force that is applied by you. Your hand. By pushing or pulling.

- Output force – The force that is applied to the object

- Also called the effort arm

- Also called the resitance arm

1st Class Lever -- The fulcrum is between the two ends

- The input and output are at the ends

input outputOrVis versa

Fulcrum

Example?

input

output

Fulcrum

Crow bar

2nd Class Lever -- The fulcrum is is at one end

- The input is at the opposite end of fulcrum

inputoutput

Fulcrum

- The output is between input and fulcrum

Example?

inputoutput

Fulcrum

Wheel Barrow

Don’t forget the other example- you have to draw it.

3rd Class Lever -- The fulcrum is is at one end again

- The output is at the opposite end of fulcrum

input output

Fulcrum

- The input is between input and fulcrum

Example?

Catapult

input

output

Fulcrum

Wheel and Axle-- A lever that rotates in a circle around a

center point or fulcrum

- There is the obvious wheel that is a wheel and axle but there are some that are not so obvious.

Center

Point

Rotation

Like this --

Central Axis

Rotation

OR like this --

Central Axis

Rotation

There does not have to be an actual wheel. It just has to spin around a central point.

OR like those

Pulley -

- Is a wheel and axle with a string, rope, chain, or belt the is pulled around the wheel part.

The Incline plane

Family

Simple Inclined Plane - - Which is . . . ?

- A Ramp

Wedge- - When you butt one ramp, - Against another

- It is a wedge.- They are always used for cutting or splitting of some kind

- Examples – Scissors, Knives,

Shears, Shovels, Spatulas, nails ect . .

Screw- - A ramp that is wrapped around a central axis

- Used for - Fasteners

- Augers

- Clamps

-Mechanical Advantage- The numerical value of

how much your force is multiplied using a machine.

- Formulas-

Input distanceOutput

Distance

Output ForceInput Force

MA=

MA=

OR

Example -

If you had a 1st class lever that you wanted to lift a rock with and the input distance was 4 feet and the output distance was only 1 foot, What is the mechanical Advantage?

Input distance

= 4 ft

Fulcrum

Output distance

= 1 ft

Input distance

= 4 ft

Fulcrum

Output distance

= 1 ft

Input distanceOutput

Distance

MA=

MA=

4 feet

1 foot= 4

That means that your force that that is pushing up is 4 times as much on the rock you are lifting. If you push with 10 lbs, you can lift 40lbs.