Physics for Scientists & Engineers & Modern Physics, 9th Ed

Mass
The SI fundamental unit of mass, the kilogram (kg), is defined as the mass of a spe-
cific platinum–iridium alloy cylinder kept at the International Bureau of Weights 
and Measures at Sèvres, France. This mass standard was established in 1887 and 
Pitfall Prevention 1.1
Reasonable Values Generating 
intuition about typical values of 
quantities when solving problems 
is important because you must 
think about your end result and 
determine if it seems reasonable. 
For example, if you are calculating 
the mass of a housefly and arrive 
at a value of 100 kg, this answer is 
unreasonable and there is an error 
somewhere.
1
We will use the standard international notation for numbers with more than three digits, in which groups of three 
digits are separated by spaces rather than commas. Therefore, 10 000 is the same as the common American notation 
of 10,000. Similarly, p 5 3.14159265 is written as 3.141 592 65.
 
Approximate Values of Some Measured Lengths
 
Length (m)
Distance from the Earth to the most remote known quasar 
1.4 3 10
26
Distance from the Earth to the most remote normal galaxies 
9 3 10
25
Distance from the Earth to the nearest large galaxy (Andromeda) 
2 3 10
22
Distance from the Sun to the nearest star (Proxima Centauri) 
4 3 10
16
One light-year 
9.46 3 10
15
Mean orbit radius of the Earth about the Sun 
1.50 3 10
11
Mean distance from the Earth to the Moon 
3.84 3 10
8
Distance from the equator to the North Pole 
1.00 3 10
7
Mean radius of the Earth 
6.37 3 10
6
Typical altitude (above the surface) of a satellite orbiting the Earth 
2 3 10
5
Length of a football field 
9.1 3 10
1
Length of a housefly 
5 3 10
2
3
Size of smallest dust particles 
, 10
2
4
Size of cells of most living organisms 
, 10
2
5
Diameter of a hydrogen atom 
, 10
2
10
Diameter of an atomic nucleus 
, 10
2
14
Diameter of a proton 
, 10
2
15