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For centuries shoes were made of leather, cloth, or wood because they help protect feet from a harsh environment- out in the woods or the concrete jungle, but they didn't provide much traction so you wouldn't slip.
In the early twentieth century companies started making shoes called "sneakers." Sneakers were made of cloth or leather upper sections with rubber soles on the bottom. (I am the only one here that remembers when NIKE came out- the company revolutionized the running world) These Sneakers gave a lot of traction and kept people from slipping down, but over time lost their tread and became slick.
This unit discusses how those sneakers became slick using ideas of Force and Motion