# Oh! My Aching Feet

…connecting force, area, and pressure? That’s some feat!

Contributed by: Catherine Little

• Systems are designed to accomplish tasks.
• All systems include an input and an output.

### Inquiry Skills Used

This activity uses scientific inquiry and experimentation activities.

### Safety Considerations

Remind students to wash their hands after handling footwear.

### Background

An important concept in this strand is the relationship between force, area, and pressure.  At this age, things like shoes become interesting status symbols to students and the fashion of the day may override comfort.  Exactly how much force is acting on our poor feet when we wear various types of shoes?

### What You Need

• Various shoes (The wider the variety the better. Start with everyday shoes and branch off into snowshoes, ballet slippers, etc.)
• Measuring devices (rulers, string, etc.)
• Calculator
• The Bata Shoe museum in Toronto has a good website: http://www.batashoemuseum.ca/ for image and text research.

### What to Do

1. Review formulae for calculating the area of various shapes (e.g., Area = length x width).
2. Introduce students to the formula used for calculating pressure (Pressure = Force / Area).
3. Choose a suitable amount of force to work with that represents a student (e.g., 500 Newtons).
4. Have students work in groups of 2-3 to measure and calculate the area of the sole and the pressure involved in wearing a wide variety of shoes.
5. Students are to record their results in a table.
6. After sharing their findings, help students identify that fluids can exist under different pressures (e.g., air in the atmosphere and air in a bicycle tire).
7. Introduce them to Pascal’s Law and then have them link what they have learned about shoes to fluids.
8. How does increasing or decreasing the area of the sole of a shoe affect the pressure on the sole?
9. How would increasing or decreasing the volume affect the pressure of the fluid?

### Where to Go from Here?

Ask students to predict the affect of increasing or decreasing temperature on the pressure of a fluid.  Students can then design an experiment to test their predictions.  Students may want to go further along the foot path and study the link between wearing certain types of shoes and foot problems.  They may want to interview a chiropodist or other foot specialist.  They may also find it interesting to interview ballet dancers about their special foot care needs.

Research why workers in various trades need to wear safety footwear. What safety footwear is required for different jobs,  e.g., lawn maintenance, construction, electrical linesman, firefighters, field technicians, and biologists)? How do these various safety footwear meet the needs of the job?

### Cross Curricular Connections

Language

• In partners or small groups, write a proposal for a shoe that will meet a specific need (i.e., football, lacrosse, polo jumping, etc.).  Include the design plan, the materials, the projected cost, the different components of the system, strategies used to be more efficient, the outline of the user guide, and a possible advertising strategy (poster, radio ad, etc).
• Create a website using text and images that demonstrates either how to calculate the mechanical advantage of various types of shoes or ways that one can make shoes more efficient.

Math

Data Management and Probability

• Create a graph to represent changes in mechanical advantage when certain factors in a mechanism are manipulated, or collect and organize discrete or continuous primary data and display the data using graphs.

### Credit Where Credit is Due

The National Science Teachers’ Association published an article called “You Can Always Tell a Dancer by Her Feet” in their January 2001 issue of Science Scope (Volume 24, Number 4).

(noscript)