Derived units:

          The units used to measure derived quantities are called derived units.

Derived units are defined in terms of base units and are obtained by multiplying or dividing one, or more base units from each other.

 Examples:

1. The unit of area (meter)² and the unit of volume (meter)³ are based on the unit of length, which is meter. Thus, the unit of length is the base unit while the unit of area and volume are derived units.
2. Speed is defined as the distance covered in unit time; therefore, its unit is a meter per second. In the same way, the unit of density, force, pressure, power, etc. can be derived using one or more base units.

 

Derived quantities and their SI units with symbols

Quantity		Unit
Name	Symbol	Name	Symbol
Speed	V	meter per second	ms-1
Acceleration	A	meter per second per second	ms-2
Volume	V	cubic meter	m3
Force	F	newton	N or (kg m s2)
Pressure	P	pascal	Pa or (N m-2)
Density	Ρ	kilogram per cubic meter	Kgm-3
Charge	Q	coulomb	C or (As)

Quick Quiz

 

1. How can you differentiate between the base and derived quantities?

 Ans: Difference between the base and derived quantities:

Base Quantities	Derived Quantities
i.    Base quantities are the quantities based on which other quantities are expressed.	i. The quantities that are expressed in terms of base quantities are called derived quantities
ii. Length, mass, time, electric current, temperature, the intensity of light | and the amount of a substance.	ii. Area, volume, speed, force, work, energy, power, electric charge, electric potential, etc.

2. Identify the base quantity is the following:

1. Speed 2. Area 3. Force  4. Distance

The distance can be considered as a base quantity because the distance is equal to the length and its unit is a meter.

1. Speed, area, and force are derived quantities because these quantities are expressed in terms of base quantities.
2. Identify the following as base or derived quantity: density, force, mass, speed, time, length, temperature, and volume.

   Base Quantities	Derived Quantities
   Length, mass, time, temperature.	Density, volume, speed, force,

    

              Ans

   

   Mini Exercise

   Volume is a derived quantity

   1L        = 1000mL

    1L       = 1 dm³

               = (10cm) ³

               = 1000 cm³

    1mL = 1 cm³

    Express 1 m³ in liters    ......... L

   Solution: -1m³ in liters=1000L