The correct option is Density = Mass/Volume; SI unit kg m-3.
Explanation
Density is a fundamental physical property that represents the quantity of mass per unit volume of a substance. It is an intensive property, meaning its value is independent of the amount of matter present.
Analysis of Definition and Units:
- Mathematical Definition: Density ($\rho$) is defined as the ratio of an object's mass ($m$) to its volume ($V$).
Formula: Density = Mass / Volume - SI Unit Derivation: The International System of Units (SI) assigns base units to physical quantities:
- The SI base unit for Mass is the kilogram (kg).
- The SI derived unit for Volume is the cubic meter (m³).
- Conclusion: By substituting these base units into the density formula, the SI unit is obtained as kg/m³ or kg m⁻³.
Evaluation of Incorrect Options:
- Density = Volume/Mass; SI unit kg m-3: Incorrect formula. Volume/Mass represents specific volume, which is the reciprocal of density.
- Density = Mass/Volume; SI unit g m-3: Incorrect unit. The gram (g) is a unit in the CGS system, not the SI base unit for mass.
- Density = Mass/Volume; SI unit kg cm-3: Incorrect unit. The cubic centimeter (cm³) is a CGS unit, not the SI unit for volume.
Key Takeaway:
Density is strictly defined as Mass divided by Volume. Its standard SI unit is kg m⁻³, derived directly from the SI base units for mass (kg) and length (m).