Units and Standards

There are 4 fundamental scientific measurements:

  • Mass
  • Length
  • Time
  • Electric Charge
The following summarizes their basic SI (International Metric System) units:
 
Fundamental Quantity

Mass

Length, distance,
displacement

Time

Charge

SI Unit

kg (kilogram)

m (metre)

s (second)

C (coulomb)

Symbol

m

 Δd

t

Q

 

Scalar vs. Vector Quantities

  • Scalar quantities express only a quantity and a unit
  • Vector quantities express a quantity, a unit and a direction

Examples:

 

Quantity Symbol Type Example
 distance Δd scalar  Δd = 10 m
displacement vector = 10 m [E]