Orbital Velocity — Prelims Strategy

Prelims Strategy

To excel in NEET questions on orbital velocity, a clear strategy is essential. First, thoroughly memorize the core formula: $v_o = \sqrt{\frac{GM}{r}}$. Understand that $r$ is the distance from the center of the central body, so if height $h$ above the surface is given, use $r = R+h$.

Also, remember the useful approximation $v_o \approx \sqrt{gR}$ for orbits very close to the surface, and the relation $GM = gR^2$. For numerical problems, pay close attention to units (convert km to m, etc.

) and powers of 10. When comparing velocities of different satellites, use ratios to simplify calculations, as $GM$ often cancels out. Be particularly careful with the square root in the formulas. For conceptual questions, always remember that orbital velocity is independent of the mass of the orbiting satellite.

Also, clearly distinguish between orbital velocity and escape velocity ($v_e = \sqrt{2} v_o$). Practice problems involving the time period of orbit ($T = \frac{2\pi r}{v_o}$) and energy considerations ($E = -\frac{GMm}{2r}$).

Trap options often involve incorrect proportionality (e.g., $v_o \propto 1/r$ instead of $1/\sqrt{r}$) or confusing orbital velocity with escape velocity. A systematic approach of identifying given quantities, writing the correct formula, and careful substitution will lead to accurate answers.