Stress in solids: pressure in fluids
Teaching Guidance
for 11-14
Snowshoes
Wrong Track: Wearing snowshoes decreases the pressure on the snow.
Right Lines: Pressure is a property of liquids and gases, but not solids. The snowshoes help you to walk on the snow because they reduce the stress applied to the snow.
Talking about stress
Thinking about the learning
Almost any example that has one solid resting on another will tend to lead to thinking leading along the Wrong Tracks.
Thinking about the teaching
Using pressure ideas to explain the behaviour of solids is so commonplace that you really need to decide as a science department on the approach that you will take (otherwise it will certainly be confusing for pupils). There is no doubt at all that the approach which we have set out here is the sensible and correct one from a physics point of view.
