Why is an object's density expressed as a combination of two units?
Answer (2)
Well, first of all, EVERY physical quantity is measured in a combination of 2 or more units, except for mass, length, time, and electric charge. ALL other units are made out of these. So it should not surprise you.
[ Example: Speed = (length) / (time) ]
Density is not the mass of a substance. It's the mass of a substance in a standard volume of it. So the density is made of the mass in any lump and the volume of that lump. That way, no matter how much of a substance you have, you can always compare the lump you have to all other substances.
Density is expressed as a combination of two units because it represents the mass of an object per unit of volume. The formula for density is Density ( ρ ) = Volume ( V ) Mass ( m ) . This allows us to compare how tightly matter is packed in different substances based on their mass and volume.
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