For vocational/technical teachers Familiarity with essential metric units, prefixes, and symbols Industrial uses Mass-weight clarification Other skills needed for specific subjects For mathematics and science teachers The ICME suggests that experiences with metric measurement for teachers and aides include the following topics: For all teachers in grades seven through twelve Personal measurements Estimations and verifications Error in measurement and approximation Travel distances Selection of appropriate units Construction and calibration of measuring instruments Practice with measuring Conversion within metric system Unit pricing practices Criteria for selection of instructional materials For vocational/technical teachers Vernier scales Metric (radial) protractors Map and scale drawing skills Mensuration formulas Instruments used in specific courses Visitation of exemplary programs For vocational/technical teachers at the senior high school level only More sophisticated instruments Conversion skills needed for specific courses For mathematics and science teachers Very small and very large units of measurement Factor label/unit analysis Map and scale drawing skills Mensuration formulas Instruments used in specific courses Visitation of exemplary programs For mathematics and science teachers at the senior high school level only Derived units as needed General physical constants Derivation of physical formulas More sophisticated instruments Conversion skills needed for specific courses The Mass-Weight Controversy In the rationale for Recommendation 2, it was noted that the word weight is often misused. Scientifically, the term weight has been associated with the concept of force. However, in common practice, the term weight has been used to refer to the concept of mass. In the U.S. Customary system, which is ostensibly a gravitationally based system of measurement, the unit pound has been defined as a mass of 0.453 923 7 kilogram. On the other hand, the SI system is an absolute system. While it might be useful to explicate the differences between an absolute system and a gravitational system, suffice it to say that in an absolute system the concepts of mass and weight are distinct and clear, as well as computationally easy; the distinctions between mass and weight in a gravitational system are not nearly as easy to perceive. It is unfortunate that the term weight has been defined as a force. In light of current practice, it would have been better originally to define weight as synonymous with mass. The confusion or misuse of the term weight is an artifact of shifting from a gravitational to an absolute system of measurement. In resolving the problems regarding use of the terms mass and weight, three possible solutions exist: 1. Use the word mass to refer to kilograms and avoid using the words weight and weigh. 2. Redefine the word weight to mean "mass"; and redefine the word weigh to mean "measure the mass of." Have scientists and others use the word force and not the word weight in referring to newtons. 3. Use the word weight to refer to kilograms and to newtons, the measurement unit for force. The measurement units used will serve to inform others of the meaning of the term weight-a mass, if kilograms; a force, if newtons. In resolving the problem of use or misuse of the term weight, the ICME has been concerned with the following: Metrication-Recommendations regarding terminology should not impede public acceptance of metrics. Effective teaching of pupils - Recommendations regarding terminology should complement effective teaching practices. Terminology that requires pupils to unlearn meanings at a later point in their studies should be avoided. Difficult concepts should be taught only when pupils' experiences have been expanded sufficiently to allow correct conceptualization. When terminology is merely a tool of communication, emphasis on technically correct terminology should follow the development of understanding. Interagency communication-Recommendations regarding terminology should facilitate communication among scientific, educational, governmental, private, and corporate agencies functioning in our economy. The changeover to the metric system will serve as an economic stimulus characterized by increased efficiency at home and in the international marketplace but only if communication is clear. The adoption of SI metrics requires a major linguistic change in the method of referring to the amount of matter in an object. Instead of a unit of measure of the gravitational force on an object, a unit of measure of the quantity of matter is used in the SI system. In short, there is no ambiguity of terms in SI metrics: the kilogram is a unit of mass; the newton, a unit of force. The kilogram is one of the seven base units of the SI system and cannot be confused with the newton, which is a unit of force that is derived from three base units (kilogram, metre, and second). During the changeover to a metric standard, many new terms can be expected to arise, not only for weight and mass but also for length, volume, temperature, and others. If all the areas of change are identified and explained at one time, the problem of public acceptance of correct weight and mass terminology will be considerably easier to solve. If the term weight continues to be used ambiguously, then the public cannot be expected to value the changeover to SI. Therefore, the ICME has chosen the first alternative above and recommends not using the term weight to refer to mass. (Skeptics insist that the public cannot make the adjustment to using new terminology. Those skeptics underestimate the intelligence of our citizens and probably do not realize the importance of the problem.) To summarize, it is clear that in day-to-day commerce the general public is interested in the measurement of mass, not force. Transactions are made on the quantity of matter being sold and not the force by which the Earth attracts the body being measured. (This is not an idle concern since the gravitational force has been found to vary by as much as 0.5 percent at different locations on the planet's surface.) Even though Homo sapiens may use measurement tools that measure force, the tools are designed and calibrated to translate force into units of mass. While an object may impart different forces on scales in different locations, the measurements registered in kilograms will be essentially constant; i.e., measurements of mass. |