Working Papers

High School Physics Revisited: Weight and
Mass from a Linguistic Point of View
rough machine translation ... [ Eng=>Jpn ]

R. Jeffrey Blair
contact information
Aichi Gakuin University, Nagoya, Japan

This paper explores the distinction between weight and mass in the Scientific Discourse Community (SDC) and relates those scientific terms to the way they are used in the General Discourse Community (GDC). In the process it describes the linguistic complexity of normal word use, tries to discover why high school physics students might find the scientific distinction confusing, and suggests a linguistic solution.

        This summer my son came back to Japan from Indiana, where he attends high school. In hopes of getting a headstart on the next year's physics class, he brought with him the textbook (Conceptual Physics by P. Hewitt), and I just could not resist taking a look. You see, math and science were my favorite subjects when I was a student. Although those interests changed at Caltech to such an extent that I graduated as a history major, I still have a fondness for mathematics and its physical applications. As I started to read through the book, the mathematical concepts were not particularly difficult to recall and master. Ideas such as

are relatively simple even for an applied linguist or English teacher such as myself. Rather, having been lulled into a scientific frame of mind as I waded into the literature, I found myself mystified by distinctions in terminology--distinctions between scientific terms and their general use counterparts. The difference in the first pair of words--speed and velocity--seemed quite clear. Later when I got to weight and mass, however, the explanation of the distinction between their general use and their scientific use seemed inaccurate and confusing. In this paper I would like to explore the proposed distinction between weight and mass and in the process discover and describe the linguistic complexity of normal word use.

Combining Speed and Direction into a Vector

        Physics is principally concerned with matter and motion. To describe matter and how it moves with quantitative precision scientists need to be able to assign numbers to the qualities represented by dichotomies such as (a) a lot and a little, (b) big and small, (c) heavy and light, and (d) fast and slow. I would like to begin with the distinction between speed and velocity to describe the fast/slow dichotomy because of (1) its clarity and (2) its relationship to acceleration and force--key concepts in the distinction between weight and mass, measures of the heavy/light dichotomy.
        In normal conversation people speak about speed and direction separately and use velocity as a synonym for speed without any specification of direction. In physics, however, speed (from Old English) designates a scalar quantity--a magnitude expressed by a single number, while velocity (from French and Latin) designates a vector quantity--both speed and direction represented as a series of numbers. The distinguishing feature is the concept of vectors. It is an alien concept in the general community, appearing only in conversations concerning mathematics, science, or engineering (applied science). This is a nice tidy linguistic solution for scientists who had combined the two simple entities of speed and direction into a single complex entity, a vector.

GDC speed
GDC velocity
SDC speed
.SDC velocity
GDC directionSDC direction

Table 1 Relationship of Terms

        Now let us turn our attention to mass and weight. According to Hewitt (1999, 49) mass is often confused with weight. The author defines mass as the "quantity of matter in an object" and weight as a "measure of the gravitational force acting on the object". He points out that weight depends on an object's location, while mass does not. Weight would be very different on the surface of the Moon (100/6 units) than on Earth (100 units). In any given place, however, weight and mass are exactly proportional to each other. This is expressed mathematically in Newton's well-known equation.

        F = G m M

        r 2

Here m and M stand for the masses of two objects. In theory, "every object in the universe attracts every other object" (Feynman, R., R. Leighton, and M. Sands, 1963, 7-1). The force of attraction, however, is so weak that it took more than a hundred years before Henry Cavendish [1731-1810] successfully demonstrated Newton's theory in a laboratory experment. In practice one mass (M) is almost always a celestial body, most commonly the Earth, while the other (m) is typically a person or common everyday object that can be directly weighed on a scale. Mass is a property of each of the objects alone. Weight, on the other hand, although we often attribute it to the smaller object, is a measure of mutual attraction and depends on the masses of both objects and the distance between their centers of mass (r).
        So where does the confusion come from? This is where a linguistic view can help. Many linguists, like other social scientists, envy the crisp clarity of the hard sciences and try their best to use scientific methods in their own work. Perhaps this is a situation where scientists could borrow back some of the precise descriptions and definitions that linguists have thus developed.


Discourse Communities
Measures of Amount
Binary Components of SDC Weight


Semantic Complexity in the GDC
SDC Weight of Moving Objects


Mental Images of the Act of Weighing
Units of Weight and Mass
Conclusions and a Linguistic Solution


        Sincere thanks to three friends from my days at California Institute of Technology--Daniel Reichel ('73, systems analyst), Rik Smoody (Ex '74, computer software), and David Brin ('73, science fiction author)--for valuable critical comments on earlier drafts and encouragement. Not all of the advice received was necessarily heeded, however, and I retain full responsibility for the final product.
        My love of mathematics was set in motion at Gunston Junior High School by a devoted teacher named Don Oliver Buttermore and accelerated by the force of an inspiring academic environment provided by the Class of 1966. Inertia has kept me going since then. This paper is gratefully dedicated to them and to my mother Rita Connelly Blair (MIT, Ex '40) and my father Robert Blair (1916-1978), who supported me in so many ways as I cruised through high school and the many detours my life took after I entered Caltech.

Points of Contact

        Any comments on this article will be welcomed and should be mailed to the author at Aichi Gakuin University, Junior College Division, 1-100 Kusumoto-cho, Chikusa-ku, Nagoya, Japan 456-0037 or e-mailed to him. Other papers and works in progress may be accessed at


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