Question 1

What is the difference between mass and weight?

Accepted Answer

Mass is the amount of matter in an object, measured in kilograms, and it stays the same everywhere. Weight is the gravitational force acting on that mass: W = mg, measured in newtons. A 70 kg person weighs 686 N on Earth (70 × 9.8) but only 114 N on the Moon (70 × 1.63), even though their mass remains 70 kg in both locations.

Question 2

What is gravitational acceleration on different planets?

Accepted Answer

Gravitational acceleration depends on a planet’s mass and radius: g = GM/r². On Earth g = 9.8 m/s², on Mars g = 3.7 m/s², on Jupiter g = 24.8 m/s², and on the Moon g = 1.63 m/s². A 10 kg object weighs 98 N on Earth, 37 N on Mars, and 248 N on Jupiter.

Question 3

How do you calculate density?

Accepted Answer

Density equals mass divided by volume: ρ = m/V, typically measured in kg/m³ or g/cm³. Water has a density of 1,000 kg/m³ (1 g/cm³), iron is 7,874 kg/m³, and air at sea level is about 1.225 kg/m³. Objects with density less than the surrounding fluid will float, which is why wood floats on water but sinks in air.

Question 4

How much would I weigh on other planets?

Accepted Answer

Multiply your mass in kilograms by the planet’s surface gravity. On Mars (g = 3.7 m/s²), a 70 kg person weighs 259 N or about 58 lbs — roughly 38% of their Earth weight. On Jupiter (g = 24.8 m/s²), the same person would weigh 1,736 N or 390 lbs. The Moon gives the lightest feeling at about 17% of Earth weight.

Question 5

What is center of gravity and why does it matter?

Accepted Answer

The center of gravity is the point where an object’s entire weight can be considered to act. For a uniform object, it’s at the geometric center. An object is stable when its center of gravity is above its base of support. A taller object with a higher center of gravity tips over more easily, which is why SUVs are more prone to rollovers than sedans.

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