Gravitational Potential — Prelims Strategy

Prelims Strategy

To excel in NEET questions on gravitational potential, a multi-pronged strategy is essential. Firstly, master the definitions and sign conventions. Always remember that gravitational potential is a scalar, always negative (with zero at infinity), and represents work done *per unit mass*.

Secondly, memorize and understand the derivations and formulas for point masses ($V = -GM/r$), spherical shells (constant inside, point mass outside), and solid spheres (parabolic inside, point mass outside).

Pay special attention to the potential at the center of a solid sphere ($-3GM/2R$). Thirdly, practice problems involving superposition. Since potential is scalar, simply add potentials algebraically for multiple masses.

Fourthly, understand the relationship between potential and field intensity ($E = -dV/dr$). This means field lines point towards decreasing potential. Fifthly, practice problems related to work done and potential energy changes.

Work done by an external agent to move a mass from point A to B is $m(V_B - V_A)$. Finally, be proficient in escape velocity calculations using $v_{\text{esc}} = \sqrt{-2V}$. Always double-check units and ensure correct sign usage, as these are common sources of error.

For conceptual questions, focus on the 'why' behind the negative sign and the scalar nature.