Introduction to Environmental Engineering Dr. Kagan ERYURUK

2 Measurement – Basic Measurables 1.What are some units of time? 2.What are some units of length (or distance)?

3 The basics What is SI? –SI stands for “Le Système international d'unités” or The International System of Units –France in 1840 legislated official adoption of the metric system and made its use be mandatory –In 1960, the General Conference of Weights and Measures adopted the International System of units (or SI), which is a particular choice of metric units. –SI units are used throughout the world except in the United States and some of the United Kingdom. –This system has seven SI base units, the SI units from which all others can be derived.

4 SI There is one key advantage of SI over English. –To change from one unit size or type to another is called a “conversion”. –It is very easy to convert from big units to small units and vice versa in metric (SI) units. –English units are not easy to convert. Can you easily convert one mile to inches?

The SI System SI Units –Base : meter –Supplementary: radian (plane angle), steradian (solid angle) –Derived: m/s 2

6 SI Base Units QuantityUnitSymbol LengthMeterm MassKilogramKg TimeSeconds TemperatureKelvinK Amount of substanceMoleMol Electric currentAmpereA Luminous intensityCandelaCd

7 SI Units and SI Prefixes A larger or smaller unit is indicated by a SI prefix -- that is, a prefix used in the International System to indicate a power of 10.

8 Try converting these … 1. 2mm =………m s =……..ms 3. 4 m 2 =……..cm m 3 =………cm 3 (cubic meters to cubic centimeters) Convert: a.12.5 kilograms into grams b meter into kilometers c.1500 kg/m3 into g/cm3

9 Measurables - derived from equations Density is defined as mass per volume, D = m/V For example, the density of a rectangular solid piece of aluminum, which occupies 50 cm 3 and has a mass of 120 grams, is calculated as follows: WidtW D = 120g/50 cm 3 D = 2.4g/cm 3

10 Temperature The Celsius scale (formerly the Centigrade scale) is the temperature scale in general scientific use. However, the SI base unit of temperature is the kelvin (K), a unit based on the absolute temperature scale. The Fahrenheit scale is at present the common temperature scale in the United States.

11 The relationship between metric units are shown below.

12 Conversion between units Within the SI and its derived quantities, conversion is done by simply noting the powers of ten. For example, what is the density in kg/m 3 of a material whose density is 3.30 g/mL? (3.3 g/mL) x (1 kg/1000 g) x (10 6 mL/ 1 m 3 )= 3.30 x 10 3 kg/ m 3

13 Conversion between units Between the SI and other systems What is the density in pounds/ft 3 of a material whose density is 3.30 g/mL?

14 Conversion between units Between the SI and other systems What is the density in pounds/ft 3 of a material whose density is 3.30 g/mL? (3.30 g/mL) x (1 lb/453.6 g) x (1mL/1cm 3 ) x (2.54 cm/in) 3 x (12in/1ft) 3 = 206 lb/ft 3

15Units English system: metric (SI): g = 32.2 ft/s 2 = in/s 2 = 9.81 m/s 2

16 Unit Conversions Convert the velocity v = 10 m/s to English units.

17 Problems 1.At sea level the weight density (weight per unit volume) of water is approx lb/ft 3. Use this value to determine the mass density of water in kg/m Pressure transducer measures a value of 300 lb/in 2. Determine the value of the pressure in Pascals. A Pascal (Pa) is one Newton (N) /m kg/m (10)6

18 Coherent Systems - equations can be written without needing additional conversion factors Coherent and Noncoherent Unit Systems Noncoherent Systems - equations need additional conversion factors Conversion Factor

19 ft/s 2 lb m lb f

20 Example of Noncoherent Unit Systems If a child weighs 50 pounds, we normally say its weight is 50.0 lbm

21 Example of Noncoherent Unit Systems If a child weighs 50 pounds, on a planet where the local acceleration of gravity is 8.72 ft/s 2

22 For example, we want to find out how many kilometers are there in mile distance.

23 Specific Gravity Specific Gravity (sp gr): density of a substance divided by the density of water at the same temperature. Specific Gravity is unitless. At normal temperature, the density of water is close to 1 g/mL. Thus, specific gravity of a substance at normal temperature is equal to the density. Density of substance (g/ml) Density of water at the same temperature (g/ml) Specific gravity =