...determining Density

DENSITY

The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume. The symbol most often used for density is ρ (the lower case Greek letter rho), although the Latin letter D can also be used. Mathematically, density is defined as mass divided by volume:

where ρ is the density, m is the mass, and V is the volume. In some cases (for instance, in the United States oil and gas industry), density is loosely defined as its weight per unit volume, although this is scientifically inaccurate – this quantity is more specifically called specific weight.

• SI unit of density is kilograms per metre cube (kg m^-3). It is a scalar quantity.
• Another common unit of density is g cm−3. 1000 kg m−3=1 g cm−3

ρ=The density of a substance does not change as you move from place to place as the mass and volume does not depend on the gravitational acceleration of the point that the object is at.

Qtn: Why does the cork float and the rock sink in water?
Ans: The density of a substance determines whether it will float or sink in different liquids (or gases).
The cork is less dense than water → it floats in water.
The rock is denser than water → it sinks in water.