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Part III: Evidence & Reasoning:
1. Make two graphs on a separate sheet of graph paper:
a. The coefficient of kinetic friction vs. force required to Begin motion.
b. The coefficient of static friction vs. force required to Maintain constant velocity.
2. Based upon your calculations which material(s) had the highest coefficient(s) of friction?
3. Which coefficient of friction (static or kinetic) would be MOST useful in choosing a material for the sole of a shoe?
Why? (Hint: look at your free-body diagram above)
Looking at the free-body diagram of a shoe we see it is still. Therefore, the most relevant coefficient of friction would
be static, since that implies that two objects are not moving relative to each other.
4. Which material would be most ideal for making a shoe sole based upon your evidence? Why?
Students don't need to be "right" here. They may choose any value they'd like as long as they have a rationale.
5. What are some other factors that could be considered when designing the sole of a shoe?
(Hint: look at the bottom of yours and your partner's shoes!!!)
Students will likely mention the texture of the shoe. Specifically knobs and divots that make up the pattern of the
outsole.
Materials
Force (N) Required to
Force (N) Required to
(Static) Coefficient of Friction
(Kinetic) Coefficient of Friction
Begin Motion
Maintain constant
velocity
Rubber & Wood Wood & Wood Sandpaper & Wood
Material of your choice
& Wood
Material of your choice
& Flooring
Claim-Evidence-Reasoning: (CER) Shoe Bottoms
Teacher Key (continued)