Units of Measurement Commonly used Units of Measurement Length - PowerPoint PPT Presentation

Units of Measurement  Commonly used Units of Measurement  Length  Mass  Time  Force  Engineering commonly uses 2 different systems of units  SI (System Internation) or Metric  US Customary or English

Units of Measurement SI US, English ft – feet Length m - meters s – seconds s – seconds Time kg – kilograms Mass slug lb – pounds Force N - newton

SI – System International  Force – Newton W  mg m g  9 . 81 2 s m  kg  1 9 . 81 2 s kg m By definition:  9 . 81 kg m N  2 s 1 2  s 9 . 81 N A body of mass of 1 kg has a weight of 9.81 N

SI Prefixes Symbol Prefix Multiplication Factor 10 9 G giga 1,000,000,000 10 6 M mega 1,000,000 10 3 k kilo 1,000 10 -3 m milli 0.001 10 -6 µ micro 0.000001 10 -9 n nano 0.000000001

US Customary - English  Mass – Slug W m  ft g g  32 . 2 2 s 32 . 2 lb  ft 32 . 2 2 s By definition: 2 lb s  2 lb s 1  Slug ft ft  1 Slug A body of weight 32.2 lb has a mass of 1 slug

Significant Figures  Generally 3 or 4 appropriate on final answer  Keep intermediate calculations in calculator  Round final answer  Examples: 4.78 47.8 0.478 4.78*10 3 4780