Reference guides as a teaching and learning strategy: Key conversion factors

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Reference guides as a teaching and learning strategy: Key conversion factors

Patrick Blessinger

Knowing how to use conversion factors is an important skill for science students. This is especially true for students in the USA, Myanmar, and Liberia, the only three countries still using some version of the antiquated British Imperial System (inches, pounds, gallons).

Nearly every country in the world officially uses the SI system of units because it is a standardized system of measurement based on the base-ten decimal system, making it much easier to understand, use, and calculate (millimeters, centimeters, meters) (Kicior, n.d.).

Although the UK (1965), Australia (1974), and Canada (1975) have officially switched over to the SI system of measurement, some British Imperial System units are still used in some places in the UK and Canada. For example, some imperial units are still used in the construction and food industries.?

The USA passed the Metric Conversion Act of 1975, but the Act did not make the SI system mandatory. Instead, conversion to SI was voluntary – it still permitted the use of archaic imperial units (now called customary units in the USA). Hence, industries had little incentive to switch to the SI system. As long as industries continued to use the outdated customary system of units, people had little incentive to learn SI. So, most students in the US do not start learning the SI system until they begin taking science courses in middle school.

NASA's Mars Climate Orbiter mission is a known example of a unit-conversion blunder. The orbiter's software expected the thruster firing commands to be in newtons (SI) for force, but the computer controlling the thrusters encoded the commands in pound-forces (customary). As a result, the orbiter entered the Martian atmosphere lower than expected and broke apart. The Mars Climate Orbiter mission cost about $125 million. This incident highlights the need for a mandatory standardized system of units across the STEM fields.

Because the USA is stuck with both systems, American students must learn both the customary and SI systems and how to convert between them. Therefore, both systems are used in math and science classes in the USA, adding complexity and confusion about units of measurement and additional work to the calculations.

I created the Key Conversion Factors reference guide to reduce confusion and simplify unit conversion calculations. These conversion factors are used with dimensional analysis, which allows one to convert from one kind of unit into another type within the same system (for example, inches to feet) or between systems (inches to centimeters).

The Key Conversion Factors guide serves as a quick reference for teachers and students when converting between the customary and SI measurement systems. It is useful to middle, high school, and university students just commencing their studies in scientific and technical fields.

This article will briefly explain how to use conversion factors for situations involving length, area, volume, mass, density, capacity, velocity, acceleration, weight, pressure, temperature, and energy. Each dimension involves a set of commonly used units. By using conversion factors, students will be able to solve problems in science with more confidence and accuracy (Cengel & Boles, 2019).

Conversions

The most easily remembered conversion factors are between units of length. These conversion factors find broad applications in most scientific calculations, where experiments and practical applications call for accuracy, including solving problems in kinematics.

Volume and density conversions are common in chemistry and physics. They are important properties of any object or substance. One example is converting cubic feet to cubic meters. These conversions will help students understand scaling and dimensionality.

Mass and weight are generally measured in kilograms or pounds, respectively. One example is the conversion factor: 1 pound = 0.453592 kilograms. Density is mass per unit volume.

The concepts of speed, acceleration, and force are at the very core of physics. Converting miles per hour to kilometers per hour will permit the solution of various types of questions regarding motion. This will enable the student to extend his or her knowledge of the forces at work in various systems.

Force is equal to mass times acceleration. The unit of measure for this quantity is called newtons. One common task in mechanics is converting the forces from one unit to another, such as pounds-force to newtons. This conversion factor is helpful in a wide range of problems involving weight and other forces in mechanical systems.

Another critical concept is pressure, which is the effect of a force over a given area. Pressure is the conversion of pounds per square inch into pascals or newtons per square centimeter, which are standard conversions in the study of gases and fluids.

Energy conversion is relevant in studies of thermodynamics or electrical systems. Conversion of calories to joules, with one calorie equaling 4.184 joules, or BTUs to joules, when one BTU is equal to 1055.06 joules, involves the transfer and transformation of thermal energy that takes place within or across systems.

One of the more common conversions students are asked to do is between different temperature scales. The most common conversion is from Celsius to Kelvin and vice versa (C + 273.15) (Serway & Jewett, 2018).

Dimensional analysis

Students often use dimensional analysis and conversion factors, which allow them to reduce complex problems into simpler ones.

In length conversion, if a student wants to know how many centimeters are in 25 inches, he/she would multiply: 25 in × 2.54 cm / 1 in = 63.5 cm.

In energy conversions, converting 150 calories into joules is quickly done by applying the conversion factor.?

150 calories × 4.184 joules = 627.6 joules

The conversions are essential in metabolism and thermodynamic problems (Giancoli, 2015).

Conclusion

The Key Conversion Factors reference guide is for students and teachers alike. It is not an exhaustive list, but it does provide quick access to many of the most essential kinds of conversions encountered in scientific study. This reference guide simplifies dimensional analysis with essential conversion factors, and students can apply these conversion factors to help them solve problems more easily.?

Conversion factors are fundamental in the development of scientific literacy and problem-solving competency. By applying conversion factors in practice, students will be better able to solve scientific problems more confidently.

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References

Cengel, Y. A., & Boles, M. A. (2019). Thermodynamics: An Engineering Approach (9th ed.). McGraw-Hill Education.

Giancoli, D. C. (2015). Physics: Principles with Applications (7th ed.). Pearson.

Kicior, A. (n. d.). Countries that don’t use the metric system. American Geography Society. Retrieved from https://ubique.americangeo.org/uncategorized/map-of-the-week-countries-that-dont-use-the-metric-system/

Serway, R. A., & Jewett, J. W. (2018). Physics for Scientists and Engineers with Modern Physics (10th ed.). Cengage Learning.

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Patrick Blessinger is a lecturer of education at SUNY (Old Westbury), a STEM teacher with NYSED, and chief research scientist for the International Higher Education Teaching and Learning Association or HETL.

Copyright ? [2024] Patrick Blessinger

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Opinions expressed in this article are those of the author and do not necessarily represent the position(s) of other professionals or any institution.