Mass as a measure of inertia

Steps:

• Recall that mass is a scalar quantity representing the amount of matter in an object.
• Identify inertia as the property of mass that resists changes in motion, per Newton's first law.
• Evaluate each option against this definition and related physics principles.
• Select the option that accurately describes mass's role in motion.

Why B is correct:

• Mass quantifies inertia, which resists changes in an object's velocity, as stated in Newton's first law of motion: an object at rest stays at rest, and an object in motion stays in motion unless acted upon by a net force.

Why the others are wrong:

• A: Mass is a scalar with magnitude only, not direction; vectors describe quantities like force or velocity.
• C: In a vacuum, acceleration due to gravity is constant (g ≈ 9.8 m/s²) and independent of mass, per Galileo's principle.
• D: Mass is invariant and does not change with location; only weight (mass times gravitational acceleration) varies.

Final answer: B