1.3 Units of measurements
*Every measurement has two parts
*Number
*Scale (called a unit)
*SI system (le Systeme International in French) based on the metric system
*Examples:
• 20 grams
• 20    k   g   = 20 X103 g
• 20    m  g  = 20 X10-3 g
• 6.63   Joule seconds
Prefix