__Lab: Measuring Coefficients of Friction__

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**Purpose:**

- To determine whether tread design affects the coefficient of static friction for running shoes

**Materials:**

- Meter stick
- Wooden board
- 7 examples of shoes

**Hypothesis:**

- I hypothesize that the tread design will affect the coefficient of static friction of the shoes.

**Procedure:**

- Collect observations of each shoe: size, heaviness, width, and a brief description of what the tread looks like.
- One by one, place each shoe on the wooden board, and raise one side until the shoe begins to slide downward. Take measurement of angle of inclination. Repeat 3 times for each shoe so as to maintain accurate data.
- Repeat step 2 measuring data for rough side of wood as well as smooth side.
- Use angle of inclination to solve for each shoe’s coefficient of static friction between its tread, and the wooden board.
- Use all data gathered to disprove or confirm hypothesis.

**Observations:**

Shoe descriptions:

- Skater shoe: mildly heavy shoe, tread is flat and worn down with wavy pattern through it
- Running shoe #1: very lightweight shoe, tread is thick and in 2 separate blobs, and also worn down to make it more flat.
- Running shoe #2: also very lightweight shoe, tread is thick and has texture, also in 2 blobs, not much tread is touching the surface of the wood.
- High heal shoe: medium weight shoe, tread is very flat, thin and in 2 sections.
- Male dress shoe #1: Heaviest shoe, tread has slight texture, but otherwise very flat and very widespread.
- Male dress shoe #2: Semi-lightweight shoe, tread has texture and is curvy.
- Sandal: Heavier shoe, tread is wavy and blocky.

Wood description: 58cm long, 30cm wide, one side is rough and other side is smooth.

Observations chart:

Shoe | Surface | Test1 | Test2 | Test3 | Test Average | Coefficient of Static Friction |

1 | Smooth | 26° | 24° | 23° | 25° | tan q =mu \tan 25=0.47 \mu = 0.47 |

1 | Rough | 53° | 54° | 53° | 53° | tan 53 = 1.32 |

2 | Smooth | 45° | 46° | 44° | 45° | tan 45 = 1.0 |

2 | Rough | 46° | 50° | 49° | 49° | tan 49 = 1.15 |

3 | Smooth | 45° | 48° | 49° | 48° | tan 48 = 1.11 |

3 | Rough | 49° | 50° | 47° | 49° | tan 49 = 1.15 |

4 | Smooth | 25° | 31° | 27° | 27° | tan 27 = 0.5 |

4 | Rough | 37° | 38° | 40° | 38° | tan 38 = 0.78 |

5 | Smooth | 42° | 41° | 43° | 42° | tan 42 = 0.9 |

5 | Rough | 53° | 54° | 52° | 52° | tan 52 = 1.28 |

6 | Smooth | 31° | 33° | 31° | 32° | tan 32 = 0.62 |

6 | Rough | 36° | 37° | 36° | 36° | tan 36 = 0.73 |

7 | Smooth | 40° | 41° | 39° | 40° | tan 40 = 0.84 |

7 | Rough | 47° | 48° | 49° | 48° | tan 48 = 1.11 |

*Test1, test2, and test3 are all the observed angles of inclination.

**Analysis:**

Through analysis of the data that I have collected in this experiment, it is apparent that it is not the tread itself that makes a change in the coefficient of static friction, but the type and heaviness of the shoe itself. Though it does provoke a very miner change, it does not prove my hypothesis to be even remotely possible given the data shown in my observations. Ways to improve the quality of this data could be if we were to lengthen the board to get a more accurate angle of inclination, or possibly having an even wider range of shoes might make a difference in results.

**Conclusion:**