Gravitational Force Calculator
Calculate gravitational force between any two masses, your weight on other planets, and the escape velocity from any celestial body.
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Gravity and Gravitation Guide
What's the key thing to understand about Newton's Law of Universal Gravitation?
F = Gm₁m₂/r², where G = 6.674×10⁻¹¹ N⋅m²/kg², m₁ and m₂ are the two masses in kg, and r is the distance between their centres in metres. Weight on Earth = mass × g, where g = 9.81 m/s² at sea level. Your 'weight' actually varies slightly across Earth's surface — it is about 0.5% less at the equator than at the poles due to Earth's rotation and slightly flattened shape (centrifugal effect and slightly larger radius at the equator).
What do I need to know about Weight on Other Planets?
Gravitational acceleration varies with planetary mass and radius. On the Moon (g = 1.62 m/s²): a 70kg person weighs 113N — about 16% of Earth weight. On Mars (g = 3.72 m/s²): about 38% of Earth weight. On Jupiter (g = 24.79 m/s²): 252% — a 70kg person would weigh about 1,735N and have extreme difficulty even standing. On the Moon, the lack of gravity and atmosphere makes daily activities drastically different — astronauts must be careful not to develop muscle and bone loss (which begins within days of exposure to microgravity, requiring dedicated daily exercise routines to slow the loss during long space missions.
What's the key thing to understand about Escape Velocity?
Escape velocity is the minimum speed needed to escape a body's gravitational pull without further propulsion: v = √(2GM/r). Earth: 11.2 km/s (40,320 km/h). Moon: 2.38 km/s. Mars: 5.03 km/s. Jupiter: 59.5 km/s. This is why it is so difficult (energetically) to leave Earth's gravity well — a rocket must accelerate to 11.2 km/s, requiring enormous fuel. The Saturn V moon rocket used more fuel in its first stage than all previous rocket launches combined.
What do I need to know about Tidal Forces and Roche Limit?
Gravitational force varies with distance — the near side of a body (like the Moon relative to Earth) experiences stronger gravitational pull than the far side, creating a tidal force that stretches the body. The Roche limit is the minimum orbital radius at which a satellite can survive without being torn apart by tidal forces — bodies orbiting within it (like Saturn's rings) are shredded into ring particles. Earth's tides are caused by the Moon's gravitational tidal force — the ocean bulges both