Page 127 - Physics

Mechanical properties of matter

Chapter Six

Mechanical properties of matter

Introduction

Study of mechanical properties of matter plays a signifi cant role in physics and
engineering. When constructing houses, bridges, and fl y-overs, the proper selection
of materials, based on their properties, is required. In this chapter, the concepts
involving elasticity, adhesion and cohesion, surface tension and capillarity will be
discussed. The competencies developed will enable you to analyse and apply the
properties of different materials found in your environment.

Think
the mechanical properties of material used in constructing bridges

Concept of elasticity

If you stretch and release a rubber band, it will return to its original shape and size. If
you compress and release a coil spring, it will resume its original length and shape.
When a rubber band is stretched, we say it is deformed because it is not in its original
shape. A coil spring is also deformed when compressed. The ability of objects to return
to its original shape after deformation is called elasticity. Thus, elasticity is the ability
of a deformed body to return to its original shape and size when the forces causing the
deformation are removed. A body with this ability is said to be elastic.

Relati onship between tension and extension of an elasti c material
When a metal is subjected to a force it undergoes deformation. The force that causes
this deformation is referred to as tension, while the extent of deformation is known as
extension. Elastic materials undergo deformation when tension is applied but regain
their original shape when the tension is released. Materials which cannot exhibit
elasticity are known as inelastic materials. Examples of elastic materials include a
rubber band and strings. A good example of inelastic material is the glass. Figure 6.1
shows some elastic materials.

(a) A rubber band tying pens (b) An extensible string of bow (c) Musical instrument drum
Figure 6.1: Elastic materials

121

Physics Form 1 Final.indd 121 16/10/2024 20:57