======Simple Machines in a Zipper======


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**Alternative titles:** The Science of Zippers
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====Summary====                   
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====Procedure====  
  - Show students a zipper and use a magnifying glass to highlight the teeth.  
  - Explain that each tooth is formed from two inclined planes, creating a wedge.  
  - Demonstrate how the wedges interlock to hold the zipper shut.  
  - Point out the zipper pull and explain that it acts as a lever.  
  - Show how moving the pull applies effort to the lever, which forces the wedge-shaped teeth together or apart.  
  - (Optional) Discuss how the spiral design of some zipper teeth resembles a screw, and compare with an actual screw.  
  - Draw a diagram on paper or a whiteboard to summarize the wedge, lever, and screw actions.



====Links==== 
  * None available

====Variations====
  * Compare different zipper types (metal vs. plastic teeth).  
  * Take apart a zipper to let students examine the individual teeth.



====Safety Precautions====
  * Avoid pulling the zipper too hard, which may break it or pinch fingers.  
  * Supervise if small parts of the zipper are detached, as they may pose a choking hazard.




====Questions to Consider====
  * How do the wedge-shaped teeth keep the zipper closed? (The inclined planes force the teeth into interlocking positions, resisting pulling apart.)  
  * Why is the zipper pull necessary instead of just pushing the teeth together by hand? (The lever allows applied force to be directed evenly across the wedges.)  
  * How is the zipper similar to other simple machines like ramps or screws? (It uses inclined planes to spread force over distance, reducing effort.)