Physics Essay

3270 Words Aug 29th, 2014 14 Pages
Measurement and Measurement Error

PHYS 1313 S06
Prof. T.E. Coan
Version: 16 Jan ’06


Physics makes both general and detailed statements about the physical universe and these statements are organized in such a way that they provide a model or a kind of coherent picture about how and why the universe works the way it does. These sets of statements are called “theories” and are much more than a simple list of “facts and figures” like you might find in an almanac or a telephone book (even though almanacs and telephone books are quite useful). A good physics theory is far more interested in principles than simple “facts.” Noting that the moon appears regularly in the night sky is far less interesting than
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(For example, Einstein’s theory of relativity is a refinement of Newton’s theory of relativity and quantitatively describes phenomena that Newton did not know about.) Physicists, as well as other scientists, give a kind of provisional assent to their theories, however successfully they might agree with experimental observation. Comfortably working with uncertainty is a professional necessity for them.

Making careful quantitative measurements are important if we want to claim that a particular physics theory explains something about the world around us. Measurements represent some physical quantity. For example, 2.1 meter represents a distance, 7 kilograms represents a mass and 9.3 seconds represents a time. Notice that each of these quantities has a number (9.3) and a unit (“seconds”). The number tells you the amount and the unit tells you the thing that you are talking about. Both the number and the unit are required to specify a measured quantity. Leaving either out makes your answer wrong! Pay attention.


There is a certain inherent inaccuracy or variation in any measurement we make in the laboratory. This inherent inaccuracy or variation is called experimental “error” and the word is not meant to imply incompetence on the part of the experimenter. Error merely reflects the condition that our measuring instruments are imperfect. This lack of perfection in our measuring procedure is to be contrasted with mistakes like

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