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Physics · Ch 1 — Nature of Physical World and Measurement

Measurement of mass

1.5.2

Measurement of mass

Mass is a property of matter -- the quantity of matter contained in a body -- and, unlike weight, it does not depend on temperature, pressure or the body's location in space. Its SI unit is the kilogram (kg), historically defined by a platinum-iridium (9:1 alloy) prototype cylinder, 3.9 cm in height and diameter (Figure 1.7), chosen specifically because that alloy resists change from environmental effects and the passage of time.

Masses studied in this course range from the electron (9.11×10−319.11\times10^{-31} kg) to the entire known universe (≈1055\approx10^{55} kg) -- Table 1.6 lists the order of magnitude across this whole span.

Measurement methods, matched to scale:

  • Ordinary masses: a common balance (like a grocer's balance), spring balance, or electronic balance. …
Figure 1.7The international 1 kg standard of mass

What this figure shows. A photograph-style illustration of the platinum-iridium (9:1 alloy) cylinder, 3.9 cm in height and diameter, that historically defined the kilogram. …

Table 1.6Range of masses
ObjectOrder of mass (kg)
Electron10−3010^{-30}
Proton or Neutron10−2710^{-27}
Uranium atom10−2510^{-25}
Red blood corpuscle10−1410^{-14}
A cell10−1010^{-10}
Dust particle10−910^{-9}
Raindrop10−610^{-6}
Mosquito10−510^{-5}
Grape10−310^{-3}
Frog10−110^{-1}
Human10210^{2}
Car10310^{3}
Ship10510^{5}
Moon102310^{23}
Earth102510^{25}
Sun103010^{30}
Milky Way104110^{41}
Observable Universe105510^{55}
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