Mass is the amount of matter in an object

• measuring tool: balance
• There are three types of balances: equal arm balances, unequal arm balances (the ones we use), and electronic balances.
• units:
• (American) slugs
• (SI) kg (fundamental unit), g, mg
• doesn't change with location (because it doesn't change with gravity)
• your mass stays the same, even during space travel

• measuring tool: scale
• units:
• (American) pounds, ounces, tons
• (SI) Newtons
• DOES change with location (because gravity can vary!)
  • changes with altitude
  • changes during space travel (your weight is 1/6 of your Earth weight on the moon!)