Final answer:
Compressive stress and strain occur when forces contract an object, causing its shortening. Examples include the columns supporting a heavy box and the top surface of a shelf loaded with heavy books.
Step-by-step explanation:
Compressive stress and strain occur when forces are contracting an object, causing its shortening and resulting in a negative change in length. For example, if a heavy box is placed on a table supported by three columns, the columns experience compressive stress due to the weight of the box. Similarly, when a long shelf is loaded with heavy books, the top surface of the shelf experiences compressive stress while the bottom surface experiences tensile stress.