Newton's Law of Universal Gravitation
Every mass attracts every other mass with a force proportional to their masses and inversely proportional to the square of the distance between them. Newton's formula is F = G(m?m?)/r^2, where G is the gravitational constant (6.674x10??? N?m^2/kg^2), m? and m? are the masses, and r is the distance between their centers. This fundamental law explains planetary orbits, tides, and the structure of the universe.
Gravity in Our Solar System
Gravity governs celestial mechanics. Earth's gravity holds the Moon in orbit and keeps us on the ground. The Sun's immense gravity keeps planets in orbit. Jupiter's strong gravity influences asteroid trajectories and protects inner planets from some impacts. Gravity decreases with distance squared-doubling distance reduces gravitational force to one-quarter. This inverse square law means gravity's influence extends infinitely but weakens rapidly with distance.
Gravity's Universal Impact
Gravitational force shapes the cosmos. It formed stars and galaxies from primordial gas clouds. It creates black holes when massive stars collapse. GPS satellites must account for both weaker gravity at altitude and relativistic time dilation. Engineers launching satellites must calculate escape velocity and orbital mechanics using gravitational principles. Tides result from the Moon's and Sun's gravitational pull on Earth's oceans, demonstrating gravity's influence even across vast distances.
Quick Tips
- Always verify units are consistent
- Use scientific notation for very large/small numbers
- Results are approximations — real conditions may vary
Frequently Asked Questions
Gravitational force F = mg increases with mass, but acceleration a = F/m = g is independent of mass. Heavier objects experience more force but have more inertia, so acceleration is the same (ignoring air resistance).
G = 6.674x10??? N?m^2/kg^2 is a fundamental constant describing gravity's strength. It's extremely small, which is why gravity is only noticeable with at least one very large mass.
The Moon's gravity pulls more strongly on the near side of Earth than the far side, creating a tidal bulge. As Earth rotates, locations pass through these bulges, experiencing high and low tides.
Newton described gravity as a force. Einstein's general relativity describes it as spacetime curvature caused by mass. Both models work for most applications, but Einstein's is more accurate for extreme conditions.
Gravity is about 10^3? times weaker than electromagnetism. A small magnet can overcome Earth's entire gravitational pull on a paperclip. The reason for gravity's weakness remains an open question in physics.