Length as a Fundamental Dimension

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 todays globally driven economy, where products are made in one place and assembled somewhere else, there exists an even greater need for a uniform and consistent way of communicating informadon about the fundamental dimension length and other related len dt 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 diferent parts of the world. 

To locate an object at pointed, with respect to the origin (point 0) of the Cartesian system, you move along the x asds by x amount (or steps) and then you move along the dashed line parallel to the axis hyy amount. Finally, you move along the dashed line parallel to the z direction by z amount. How would you get to pointed usii the Cylindrical or Spherical systeno plain. 

All of us, at one time or another, have experieoced not knowit vdrrae we ate goii. In other words, we were losd The smarter ones among us use a map or stop and ask someone for direcrions and distances (x and y coordinate) to the desired place. An example of using a map to locate a place is shown in F ure 7.2. Coordinate systems are also int rated into software that drives computer numerically controlled (CNC) machines, such as a milling machine or a lathe that cuts materials into specific shape. 

Now that you understand the importance of the length dimension, let us look at its divisions or units. There are several systems of units in use in engineering today. We will focus on two of thee systems the International System of Units (SI) and the United State Customary units. The unit of length in SI is the meter (m). We can use the mulriple and fracrions of this unit according to Table 6.2. Common multipliers of the meter are micrometer (/tm), millimeter (mm), centimeter (cm), and kilometer (km). Recall fiom our discussion of units and mulriplicarion 

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