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# Simple Machines

## Introduction to six different devices that make work easier by changing a force.

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Practice Simple Machines

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Screw Ups and Downs

### Screw Ups and Downs

Credit: Shelah
Source: http://www.flickr.com/photos/gosheshe/3510724297/
License: CC BY-NC 3.0

Poor screws. They have a bad reputation. After all, “screwing up” means “making a mistake.” But screws are actually very useful simple machines.

#### The Back Story

• A screw is an inclined plane that is wrapped around a central axis. Most screws, like those pictured above, are used to hold things together. Screws have many other uses as well.
• Credit: Simon Brass
Source: http://www.flickr.com/photos/dogbomb/527733767/
License: CC BY-NC 3.0

The corkscrew is used to remove the cork in wine bottles [Figure2]

• Watch this clever student video to see some other examples of screws and how they are used:

#### Can You Apply It?

At the links below, learn more about screws and see additional examples of screws. Then answer the questions that follow.

1. Describe the screw.
2. State two general uses of screws.
3. Describe the screws in the pictures below, and explain how the screws are used.
1. Credit: Richard Koch
Source: http://commons.wikimedia.org/wiki/File:Spiral_Staircase_in_the_Presbytere_New_Orleans_1934.jpg
License: CC BY-NC 3.0
2. Credit: Scott Ehardt
Source: http://commons.wikimedia.org/wiki/File:Crest_toothpaste.jpg
License: CC BY-NC 3.0
3. Credit: Brianiac
Source: http://commons.wikimedia.org/wiki/File:Screws.jpg
License: CC BY-NC 3.0
4. The device sketched below is called Archimedes’ screw. It is used to draw water out of a body of water such as a pond. Based on your knowledge of screws, explain how Archimedes’ screw works.

Credit: lanmacm
Source: http://commons.wikimedia.org/wiki/File:Archimedes_screw.JPG
License: CC BY-NC 3.0

5. You’ll have a better understanding of the screw and how it is related to the inclined plane if you make a model screw. Do the activity at the second link above. Then answer the questions listed at the bottom of the Web page under “Things to think about during the experiment.”

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