Everything Science Grade 12

CHAPTER 7. MECHANICAL PROPERTIES OF MATTER 7.2

Brittle material

Force

extension

fracture

Figure 7.2: A hard, brittle substance

This graph shows the relationship between forceand extension for a brittle, but strong
material. Note that there is very little extensionfor a large force but then the material
suddenly fractures. Brittleness is the property of a material that makesit break easily
without bending.

Have you ever droppedsomething made of glass and seen it shatter? Glass does this
because it is brittle.

Plastic material

extension

Force

Figure 7.3: A plastic material’s response to an applied force.

Here the graph shows the relationship betweenforce and extension fora plastic mate-
rial. The material extends under a small force but it does not fracture easily, and it does
not return to its originallength when the force isremoved.