As an engineering student,you also need to develop a keen awareness of your
surroundings.In this chapter,we will investigate the role of length,area,and vol-
ume along with other length-related variables in engineering applications.You will
learn how these physical variables affect engineering design decisions.The topics
introduced in this chapter are fundamental in content,so developing a good grasp
of them will make you a better engineer.You may see some of the concepts and
ideas introduced here in some other form in the engineering classes that you will take
later.The main purpose of introducing these concepts here is to help you become
aware of their importance and learn to look for their relation to other engineering
parameters in your future classes when you study a specific topic in detail.
Table 6.7 is repeated here to show the relationship between the content of
this chapter and other fundamental dimensions discussed in other chapters.
7 7..1 1 LLeennggtthh aass aa FFuunnddaammeennttaall DDiimmeennssiioonn
When you walk down a hallway, can you estimate how tall the ceiling is? Or how wide a door
is? Or how long the hallway is? You should develop this ability because having a “feel” for dimen-
sions will help you become a better engineer. If you decide to become a design engineer, you
will find out that size and cost are important design parameters. Having developed a “feel” for
the size of objects in your surroundings enables you to have a good idea about the acceptable
range of values when you design something.
As you know, every physical object has a size. Some things are bigger than others. Some
things are wider or taller than others. These are some common ways of expressing the relative size
of objects. As discussed in Chapter 6, through their observation of nature, people recognized the
need for a physical quantity or a physical dimension (which today we calllength) so that they
could describe their surroundings better. They also realized that having a common definition for
a physical quantity, such as length, makes communication easier. Earlier humans may have used
a finger, arm, stride, stick, or rope to measure the size of an object. Chapter 6 also emphasized the
need for having scales or divisions for the dimension length so that numbers could be kept simple
and manageable. Today, we call these divisions or scalessystems of units. In this chapter, we will focus
our attention on length and such length-related derived quantities as area and volume.
Length is one of the seven fundamental or base dimensions that we use to properly express
what we know of our natural world. In today’s globally driven economy, where products are
made in one place and assembled somewhere else, there exists an even greater need for a uni-
form and consistent way of communicating information about the fundamental dimension
length and other related length variables so that parts manufactured in one place can easily be
combined on an assembly line with parts made in other places. An automobile is a good example
of this concept. It has literally thousands of parts that are manufactured by various companies
in different parts of the world.7.1 Length as a Fundamental Dimension 161
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