Units and Standards

1. Units and Standards

There are 4 fundamental scientific measurements: Mass, Length, Time, and Electric Charge

The following table summarizes their basic SI (International Metric System) units 

Fundamental Quantity Mass Length, distance,
Time Charge
SI Unit kg (kilogram) m (metre) s (second) C (coulomb)
Symbol m  Δd t Q


2. Scalar vs. Vector

Scalar quantities express only a quantity and a unit

Vector quantities express a quantity, a unit and a direction


Quantity Symbol Type Example
 distance Δd scalar  Δd = 10 m
displacement vector = 10 m [E]
Note the arrow on the symbol for a vector  .
It symbolizes the direction property of the vectory.