Measurement, Units and the SI System

Name: Measurement, Units and the SI System
Author: StemPy Lab

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.

3 lessons, about 1 h 20 min3 simulations12 problems6 practice questionsPython in every lesson

Created by StemPy Lab

Course outline (3 lessons)

Lesson 1about 30 min
Physical quantities and the SI units
A physical quantity is something we can measure: a number times a unit. The SI system has seven base quantities, each with its base unit (metre, kilogram, second, ampere, kelvin, mole, candela); every other unit is derived from them, as $1\ \text{N} = 1\ \text{kg m s}^{-2}$ . Since 2019 the base units are fixed by constants of nature.
1 simulation2 practice questions1 Python program4 problems1 question set
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Lesson 2about 25 min
SI prefixes, conversion of units and orders of magnitude
A prefix multiplies a unit by a power of ten (kilo $10^3$ , milli $10^{-3}$ , micro $10^{-6}$ , nano $10^{-9}$ ), and it belongs to the unit with its power: $1\ \text{cm}^2 = 10^{-4}\ \text{m}^2$ . To change a unit, multiply by a ratio equal to one and check that the old unit cancels. Scientific notation writes a number as $a \times 10^n$ with $1 \le a < 10$ ; the order of magnitude is the nearest power of ten.
1 simulation2 practice questions1 Python program5 problems1 Python lab
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Lesson 3about 25 min
Measuring very large and very small lengths, masses and times
Lengths in nature run from about $10^{-15}\ \text{m}$ (a nucleus) to $10^{26}\ \text{m}$ (the visible universe), so most are measured indirectly. Parallax gives a far distance as $D = b/\theta$ with $\theta$ in radians. An oil film one molecule thick gives the size of a molecule. Atoms are weighed in atomic mass units, $1\ \text{u} = 1.66 \times 10^{-27}\ \text{kg}$ , and atomic clocks keep time.
1 simulation2 practice questions1 Python program3 problems1 Python lab1 note
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Measurement and Units: Practice Paper

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Measurement, Units and the SI System

Course outline (3 lessons)

Physical quantities and the SI units

SI prefixes, conversion of units and orders of magnitude

Measuring very large and very small lengths, masses and times

Test Your Learning

Your teacher

Discussion (0)