Gravitation — Visual Guide — Summary

Diagram 1 — Variation of g with Altitude and Depth

Distance from surface g value 0 Surface g (surface) Depth (linear) Altitude (inverse-square) Centre Below surface (depth) Above surface (altitude)

Reading the diagram: Moving left from the surface toward Earth's centre, g decreases linearly (dashed orange line). Moving right from the surface upward, g decreases by the inverse-square law (solid dark line). The depth curve is always gentler than the altitude curve for the same fractional distance.

Diagram 2 — Satellite Energy Relationships

Quantity	Formula	Sign	Ratio
Kinetic Energy (KE)	$GMm / 2r$	+	$1$
Potential Energy (PE)	$-GMm / r$	−	$-2$
Total Energy (E)	$-GMm / 2r$	−	$-1$

Rule: $|PE| = 2 \times KE$ ; $|E| = KE$ . A satellite losing total energy (more negative E) moves to a lower orbit with higher orbital velocity — a counterintuitive NEET trap.

Diagram 3 — Kepler's Second Law (Equal Areas)

Sun P A Fast (small $\Delta t$) Slow (same $\Delta t$) Both shaded areas are equal — Kepler's 2nd Law