About this experiment
The same load produces different pressure when spread over different areas. Widen the contact pad and watch the pressure markers become less concentrated. Use the inverse curve to explain snowshoes, broad foundations and sharp tools, while keeping force separate from pressure.
Learning goals
- Investigate how contact area affects contact pressure while controlling the other variables.
- Use the graph and numerical readings to test a prediction.
- Explain the physical assumptions and where this model stops applying.
How to use it
- 1Set force to 200 N and area to 100 cm². Verify pressure is 20 kPa.
- 2Double contact area without changing force. Predict the new pressure.
- 3Save the curve, double force and compare pressure at the same area.
- 4Set force to zero. Why is the entire curve on the horizontal axis?
The model
Assumptions
- The normal force is uniformly distributed over the entered flat contact area.
- The diagram shows a pad cross-section with width proportional to the square root of area. Deformation and material failure are not calculated.
Try this in class
- Q1What pressure does 600 N exert on 300 cm²?
- Q2Why does doubling both force and area leave pressure unchanged?
Frequently asked questions
Is this the pressure at every point?
It is average contact pressure. Real contact pressure can vary near edges or on rough surfaces.
Why does the curve rise so sharply at small areas?
Pressure is inversely proportional to area. The model never allows zero area, where the expression would be undefined.