Jan. 17, 2006

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     When you think of machines you probably think of cars, power saws, airplanes...or anything with a motor. However, not all machines need a motor to make them run. Do you know that hammers and nails, scissors, bottle openers, and tennis racquet are machines?

And they don't need any other kind power to work besides a person!

Are they machines? Yes... because they do work.
These machines are called SIMPLE MACHINES.

There are 6 simple machines and they all do work. They are:

You are doing work when you use a force to cause motion.

This kind of work work has 2 parts:
1. Force needed to do the work and
2. far the force is used.

Here's an example: If you want to put your pet elephant on the kitchen table you must do some work, that is, you need a force to lift the elephant a distance, to the top of the table. If you want to move 2 elephants at the same time, you must do more work.

Simple Machines help us

cut, fasten, split, lift, pull, go faster, increase elevation of heavy things, change the direction and /or increase the force.
  The Franklin Institute has more information.
Table of Simple Machines
Type of Simple Machine
Description (pictures)
LEVER -a stiff bar that turns on a point, called the fulcrum. A lever trades distance for force or force for distance, that means you use less force over a greater distance or more force over a shorter distance. More... seesaw, crowbar, claw hammer, bottle opener examples
Every lever has 3 parts:

1. Resistance Force or Load, or What you are trying to move or lift.
2. Effort Force or The Work done on the Lever.
3. Fulcrum or A fixed pivot point

There are different kinds of levers depending on the placement of the fulcrum:
The fulcrum can be between the force and what you want to move. (seesaw, crowbar)
The fulcrum can be at one end, the force at the other end, and what you want to move in the middle. (bottle opener)
The fulcrum can be at one end, the force in the middle, and what you want to move at the other end. (tennis racquet)

Sometimes 2 levers are put together like scissors and pliers. The Elements of Machines .

Follow a modern team as they build a medieval weapon, then play "Destroy the Castle"

Inclined plane for a wheelchairINCLINED
-a sloping surface, such as a ramp, used to lift heavy loads with little effort. The inclined plane does not move. It works by allowing less force but over a greater distance. More... ramp, ladder, stairs, escalator Examples
FactThe inclined plane and rollers were used in building the Pyramids in Egypt. Ramps over one mile long were used to move and place 2.5 million limestone blocks weighing up to 70 tons each.
WEDGE Wedge -inclined plane that tapers to a sharp edge A wedge is really two inclined planes joined back to back. A wedge changes the direction of the force. A wedge moves. More... nail, chisel, knife, saw, ax, doorstop, pins examples

Wedges can be forced between two things to hold them tightly together, like nails or a doorstop. A knife or a pin is a sharpened wedge.

A Bicycle is made with simple machinesWHEEL
and AXLE

-a wheel connected to a rigid rod. It can be used to increase force and to increase distance. More...

Gears are special kind of Wheel and Axle.

door knobs, car wheels , water faucets, airplane propeller, pedals on a bike examples
A door knob uses a larger "knob" to turn a smaller rod. You trade distance for force. In a bicycle you trade force for distance. By turning the bicycle axle with a pedal you get more distance (or speed) as the larger wheel turns.
PULLEY    A pulley

-a small wheel with a grooved rim that holds a rope. A fixed pulley changes only the direction of the force but not the force, distance or speed. More...

opens a curtain or mini-blind, lifts a flag on a flag pole, examples
Instead of lifting up, you can pull the rope down and lift the load down using your body weigh. A pulley is also wheel that turns around an axle.
SCREW    A Screw      -an inclined plane wrapped around a cylinder. The threads of a screw form a tiny "ramp" that goes around the screw. A screw allows you to use less force, and it changes the direction of the force. More... meat grinder, jar and lid, piano stool, helicopter blade, boat propeller examples
Nuts and bolts ( a type of screw) allow you to fasten things together. Almost every machine built has some form of screw to fasten it together.

Some tools have two or more simple machines working together. For example: scissors are 2 levers joined at fulcrum AND the blades are wedges. A can opener is a lever and a wedge. Can you think of more?

A DaVinci Drawing
Visit this site to learn about the great inventor, Leonardo da Vinci, who was not only a painter but who also had a fascination with machines.

Just remember every time you use a tool to do work you are using a simple machine. It can be a repair tool, gardening tool, kitchen tool, or tools you use to play games like croquet or baseball.
If you are INCLINED to learn more, click these links:
Links to more information     Vocabulary       References
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