1. Engineering Fundamentals and Problem Solving, 6e
Chapter 7
Dimensions, Units and Conversions

2. Chapter Objectives
Identify physical quantities in terms of dimensions and units
Differentiate between fundamental and derived dimensions
Understand the use of non-SI dimensional systems (gravitational and absolute)
Recognize base, supplementary, and derived SI units

3. Chapter Objectives – cont’d
Apply the appropriate SI symbols and prefixes
Describe the relationship between U.S. Customary, Engineering System, and SI
Systematically convert units from one system to another
Use knowledge of dimensions and units, along with conversion rules, in the solution of engineering problems.

4. Progress towards Metrification
Engineers in the U.S. must be prepared whatever system of units they encounter.
With a large French Canadian population, Canada has adopted the metric system.
Canadian highway signs

5. Dimensions Independent of units Fundamental or derived
Absolute system is based on mass (no gravity)
Gravitational system is based on force

6. SI Units and Symbols SI Units fall into 3 categories Base Units
Supplementary Units
Derived Units

7. SI Base Units 7 Base Units
Can be reproduced anywhere in the world (except kg)

8. SI Supplementary Units
May be considered base or derived units
Radian is commonly used. Steradian less so.
Radians are dimensionless
arc length = radius
1 Radian: Angle when arc length = radius
radius

9. SI derived units with names
Formed by combining
Base
Supplementary or
Other derived units

10. SI derived units without names
Some derived units have no special SI unit names or symbols

11. Non-SI units accepted for use in U.S.
Certain units outside SI are accepted for use with SI in the U.S. even though they diminish the system’s coherence.

12. Unit Prefixes

13. Significant Figures
SI prefix notations can be used to denote intended significance
Distance Precision # of significant figures
km to m 5
10.00 km to m 4
10.0 km to m 3
10 km to m 1

14. Significant Figures
Scientific notation can be used to denote intended significance
Distance Precision # of significant figures
x 104 m to m 5
1.000 x 104 m to m 4
1.00 x 104 m to m 3
1.0 x 104 m to m 2
1 x 104 m to m 1

15. Greek Alphabet