What is the difference between mass and weight, and how does gravity affect weight on different planets?

• A. Mass is the amount of matter in an object; weight is the gravitational force on that mass, and it remains constant regardless of the planet.
• B. Mass is the amount of matter; weight equals mass times gravity, and gravity is the same on all planets.
• C. Mass changes with gravity, and weight is the inertia of the object.
• D. Mass is the amount of matter; weight is the gravitational force on that mass, which varies with planet's gravity.

Answer: (D)

Mass is the amount of matter in an object, while weight is the gravitational force acting on that mass. The key idea is that mass stays the same no matter where you are, but weight changes with gravity. On different planets, gravity varies, so the same mass experiences a different downward force, which means weight differs even though the mass is unchanged. The relationship is W = m × g, where g is the planet’s gravitational acceleration. For example, a 70 kg person weighs about 686 N on Earth (70 × 9.8), but on the Moon (g ≈ 1.62 m/s²) they’d weigh about 113 N, and on Mars (g ≈ 3.71 m/s²) about 260 N. The other statements fail because they either claim weight stays constant, gravity is the same everywhere, mass changes with gravity, or weight is inertia; none of those describe how gravity actually affects weight.