In the SI system, what is the basic unit of mass?

In the International System of Units (SI), the basic unit of mass is the kilogram. The kilogram is defined as the mass of a specific platinum-iridium cylinder kept at the International Bureau of Weights and Measures. This definition is pivotal as it provides a standard that can be replicated worldwide, ensuring consistency in scientific measurements and applications.

Other units mentioned, such as newtons, are units of force, reflecting the interaction of mass with acceleration according to Newton's Second Law (force equals mass times acceleration). Cubic metres refer to a unit of volume, measuring space rather than mass. Pounds are a unit of mass commonly used in the Imperial system, but they are not part of the SI system. Therefore, the appropriate answer that aligns with the SI system for mass is, indeed, the kilogram.