Definition:
Gravity is a fundamental force of nature that attracts two
bodies with mass toward each other. It's responsible for the
structure and behavior of the universe on large scales.
🧲 Key Concepts
● Universal Law of Gravitation (Newton):
F=Gm1m2r2F = G \frac{m_1 m_2}{r^2}F=Gr2m1m2
○ FFF = gravitational force
○ GGG = gravitational constant
(6.674×10−11 Nm2/kg26.674 \times 10^{-11} \,
\text{Nm}^2/\text{kg}^26.674×10−11Nm2/kg2)
○ m1,m2m_1, m_2m1,m2= masses of the objects
○ rrr = distance between their centers
● Weight vs. Mass:
○ Mass is the amount of matter in an object (kg) –
constant everywhere.
○ Weight is the gravitational force on an object:
W=mgW = mgW=mg
where ggg ≈ 9.8 m/s² on Earth.
🌌 Gravity in Space
● Orbits: Gravity keeps planets in orbit around stars,
moons around planets, etc.
● Tides: Caused by the gravitational pull of the Moon
and the Sun on Earth's oceans.
● Free Fall: All objects fall at the same rate in a vacuum,
regardless of mass (Galileo's experiment).
🧠 Einstein’s Theory of General Relativity
● Gravity isn't just a force – it's the curvature of
space-time caused by mass.
● Massive objects like stars and planets bend the space
around them.
● Confirmed by phenomena like gravitational lensing and
time dilation near massive bodies.
🚀 Applications
● Astronomy: Predicting planetary motion, black holes,
galaxy formation.
● Engineering: Designing satellite orbits, space
missions.
● Geophysics: Studying Earth’s shape, tides, and
internal structure.
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