Screw 

 

Screw:  A screw is a simple machine that is made from another simple machine.  It is actually an inclined plane that winds around itself.  A screw has ridges and is not smooth like a nail.  Some screws are used to lower and raise things.  They are also used to hold objects together.
 

The girl in this picture is taking a lid off of a jar.  Jars use simple machines to hold the lids on the top.  When you turn the lid, it raises or lowers. 

Where would I find an example of a screw?

 

Try this experiment!

Materials:
    Nine inch paper square, pencil, tape, marker, tabletop
Procedure:
    Cut the square in half to make a right triangle.  Use the marker to outline the diagonal side of the triangle.  Now place the paper face down on the table.  Place the pencil on one of the short sides of the triangle.  Wrap the pencil around the triangle.  Use the tape to keep it in place.
Things to think about during the experiment:
-What simple machine is the right triangle?
-What simple machine was created when you wrapped the pencil around the triangle?
-Name some examples of this machine.
Conclusion:
    You made a screw out of an inclined plane when you wrapped the triangle around the pencil.
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