Question

What is the SI unit of density?
A. $g$ $c{m^{ - 3}}$
B. $g$ ${m^{ - 3}}$
C. $kg$ ${m^{ - 3}}$
D. $kg$ $c{m^{ - 3}}$

Answer 1

Hint: The word SI unit stands for Systeme international which governs the standard units of quantities throughout the world. Formula for density is, $Density = \dfrac{{Mass}}{{Volume}}$. SI unit of mass is Kg and SI unit of volume is litre or ${m^3}$.

Complete step-by-step answer:
SI unit is an international system of measurements that are used universally in technical and scientific research to avoid the confusion with the units.
Let us see how we can find the SI unit of any measurable quantity.
First of all, there are seven basic units in SI system:
-Kilogram (kg) for mass.
-Meter (m) for distance.
-Second(s) for time.
-Kelvin (K) for temperature.
-Ampere (A) for current.
-Mole (mol) for the amount of a substance.
-Candela (cd) for luminous intensity.

Now let us focus on how to find the SI unit of density.
For that we need to find the SI unit of Mass and Volume.
The SI unit for Mass is Kg as per the SI system.
For the SI unit for Volume, we know that formula of volume $ = length \times breadth \times height$ .
Length, breadth and height all are distances therefore,
SI unit of volume $ = m \times m \times m = {m^3}$ .
Now, density is basically the mass of the unit volume of a substance.
Let us see the formula for density,
 $Density = \dfrac{{Mass}}{{Volume}}$
The SI unit for Mass is Kg as per the SI system.
We also know that the SI unit for Volume is ${m^3}$ .
Therefore, the SI unit of density $ = \dfrac{{kg}}{{{m^3}}}$
Hence we can conclude that the SI unit for density is $kg/{m^3}$ or we can write it as $kg$ ${m^{ - 3}}$ .

So option C is the correct answer.

Note: Keep in mind the relation between density, mass and volume. Remember all the seven basic SI units given in the SI system. Density of an object also depends upon temperature which is not shown in the mathematical relation used here. Higher temperature constitutes less density and vice versa. For example, hot air rises up because of less density than cold air.