Units and Measurements
Every law of physics is a statement about numbers that we measure. How long is a table, how heavy is a bag, how long does a swing take? A number alone means nothing, so we write it with a unit, and no measurement is ever exact, so we also say how far we can trust it. In this chapter we learn the SI units, how to read an instrument, how to write an answer with the right number of digits, and how the dimensions of a quantity can check an equation. Python helps us calculate, simulate and test.
Part of Physics · High School (11–12) (chapter 1)
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Measurement, Units and the SI System
A friend says that a road is 5 long and a bag is 3 heavy. You cannot picture either, because there is no unit. In this course we find why physics needs units, we learn the seven base units of the SI system and their prefixes, we change from one unit to another, and we see how people measure a distance as small as an atom and as large as a star.
Accuracy, Errors and Significant Figures
Measure the same pencil ten times, and you may get ten slightly different numbers. In this course we find why, we learn to say how accurate and how precise a result is, we read a vernier callipers and a screw gauge, we find the error in a result that comes from several measurements, and we write an answer with the right number of significant figures.