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# 2.1: Investigating Static Forces in Nature: The Mystery of the Gecko

Difficulty Level: At Grade Created by: CK-12

Activity: Sole Impression

Slide 2

Indicate the relative amount of contact between each shoe and the surface. For each shoe, circle one answer and provide a reason for your answer.

Shoe on left:

Most Contact Some Contact Least Contact

Shoe in middle:

Most Contact Some Contact Least Contact

Shoe on right:

Most Contact Some Contact Least Contact

______________________________________________________________

______________________________________________________________

What could be done to see more detail and improve your responses?

______________________________________________________________

______________________________________________________________

Slide 3

Here are the same shoes, only closer up. Based on this close up view, circle one answer and provide a reason for your answer. Label the contact points on the image.

Shoe on left:

Most Contact Some Contact Least Contact

Did your response change from image 2.1? Why or why not?

______________________________________________________________

______________________________________________________________

Shoe in middle:

Most Contact Some Contact Least Contact

Did your response change from image 2.1? Why or why not?

______________________________________________________________

______________________________________________________________

Shoe on right:

Most Contact Some Contact Least Contact

Did your response change from image 2.1? Why or why not?

______________________________________________________________

______________________________________________________________

Slide 4

Looking at the sole of the shoe, rank the amount of contact. Label the contact points on the image.

Shoe on left:

Most Contact Some Contact Least Contact

Because:

______________________________________________________________

Shoe in middle:

Most Contact Some Contact Least Contact

Because:

______________________________________________________________

Shoe on right:

Most Contact Some Contact Least Contact

Because:

______________________________________________________________

Sole Impression

Slide 5

Determine the ratio of the contact area of your shoe to the total area. Use the following materials/procedure.

Materials:

• One shoe per group that you do not mind getting dirty
• Tray with finely ground sidewalk chalk, charcoal, or tempera paint with rollers (use a color other than white)
• Graph paper

Procedure:

1. Depending on the supplies provided by your teacher, cover the bottom of the shoe with ground up chalk,charcoal, or tempera paint. Make sure that the entire sole of the shoe is covered with the substance.

2. Make an impression with the shoe onto graph paper by pressing the shoe firmly onto the paper.

3. Use the counting-squares method for determining the areas. First, count the total number of squares enclosed by the perimeter of the sole of the shoe. Second, count the number of squares that have sidewalk chalk on it. \begin{align*}^{**}\end{align*} If half or more of the square is covered with chalk, count the square.\begin{align*}^{**}\end{align*}

4. Determine the ratio by dividing the amount of the surface covered with chalk (contact area) with the total area of the sole of the shoe. Use the space below for your calculations. Make sure you include units of measure with your calculations.

Results:

Contact Area

Total Surface Area

Collect data for five other groups and use this space to complete a data table comparing the ratios of contact area to total area of various shoes in your class:

Student/Group (Name) Shoe Type (tennis shoe, etc.) Ratio

Graph Your Comparisons (Ratio of contact to total area vs. Shoe Type) Be sure to label your graph properly.

1. Which of the shoes had the highest contact area to total area ratio?

1a. Describe the surface of the shoe.

2. Which of the shoes had the lowest contact area to total area ratio?

2a. Describe the surface of the shoe.

2b. How do these results compare with your observations on 2-1 and 2-2.

3. If you included all the soles’ nooks and crannies, which shoe would probably have the most total surface area? (NOT RATIO!)

4. What type of sole material (soft or hard) could come into the most contact with the total surface? Why?

5. Based on your examination of different shoe soles, what are your ideas about the surface of a gecko’s foot, and what makes you think that way?

Investigating Static Forces in Nature: The Mystery of the Gecko

Lesson 2: What Do We Mean When We Speak About Surfaces in Contact?

Student Journal

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