I've been working on a revised set of Safer Geography Activity (Command) Cards this past few days. One goal that I had was to ensure that wherever possible, the "Explanation" really explained, using scientific principles. That goal sent me off delving into physics from time to time.
As a future objective I plan to create a second set of these cards for older children, and I want this first set to serve as a scientific foundation for some of the directions I'll be taking there.
Here's what I came up with for Solids Can Be Rigid, Elastic or Plastic:
If additional force (but less than the solid’s yield strength) is applied, then the solid deforms, but returns to its original shape when the force is removed. Its particles are temporarily displaced. The solid is then said to be elastic.