How is mass defined in mechanics?

Mass in mechanics is defined as a measure of the amount of matter in an object, and it is typically quantified in kilograms (kg). This definition is foundational in physics because mass is a scalar quantity that does not change regardless of the object's location, whether it is on Earth, the Moon, or in space.

Mass is critically important because it directly influences the gravitational force experienced by an object and its resistance to acceleration when a force is applied, according to Newton's second law of motion (F=ma, where F is force, m is mass, and a is acceleration). This understanding sets mass apart from other concepts such as weight, which is dependent on gravitational force and varies with location.

The other answer choices do not accurately reflect the concept of mass. For example, volume relates to the space an object occupies, but does not correlate directly with how much matter is present. Weight is the force that results from gravity acting on mass; hence, dividing weight by gravitational acceleration gives mass, but this is not the primary definition of mass itself. Finally, force is an entirely different physical quantity that describes interaction, not the quantity of matter.