Introduction - Mathematics and Statistics for the Environment - page 13

TABLE 1.3 (continued)
Conversion Factors by Unit Category

Factor Metric (SI) or English Conversions

Radiation and Dose Related Units

1 Bq (becquerel) 1 radioactive disintegration/second

2.7 × 10 -11 Ci (curie)
2.7 × 10 -8 (millicurie)

1 Ci (curie) 3.7 × 10 10 radioactive disintegration/second

3.7 × 10 10 Bq (becquerel)
1000 mCi (millicurie)

1 Gy (gray) 1 j/kg (joule/kilogram)

100 rad
1 Sv, unless modified through division by an
appropriate factor, such as Q or N

1 mCi (millicurie) 0.001 Ci (curie)

3.7 × 10 10 radioactive disintegrations/second
3.7 × 10 10 Bq (becquerel)

1 rad 100 ergs/g (ergs/gram)

0.01 Gy (gray)
1 rem, unless modified through division by an
appropriate factor, such as Q or N

1 rem 1 rad, unless modified through division by an

appropriate factor, such as Q or N

1 Sv (sievert) 1 Gy, unless modified through division by an

appropriate factor, such as Q or N

1.4 CONVERSION FACTORS: PRACTICAL EXAMPLES
Sometimes we have to convert between different units. Suppose that a 60-inch piece of pipe is
attached to an existing 6-foot piece of pipe. Joined together, how long are they? Obviously, we can-
not find the answer to this question by adding 60 to 6, because the two lengths are given in different
units. Before we can add the two lengths, we must convert one of them to the units of the other.
Then, when we have two lengths in the same units, we can add them.
To perform this conversion, we need a conversion factor . In this case, we have to know how
many inches make up a foot: 12 inches. Knowing this, we can perform the calculation in two steps:

1. 60 in. is really 60/12 = 5 ft

2. 5 ft + 6 ft = 11 ft

DID YOU KNOW?

Units and dimensions are not the same concepts. Dimensions are concepts such as time, mass,
length, or weight. Units are specific cases of dimensions, such as hour, gram, meter, or pound.
You can multiply and divide quantities with different units: 4 ft × 8 lb = 32 ft-lb, but you can
add and subtract terms only if they have the same units. So, 5 lb + 8 kg = no way!