Kepler S Second Law Law Of Areas — the NEET Physics formula with its derivation, variables, validity constraints and worked solver.
Kepler's Second Law (Law of Areas) Applies to any object moving under the influence of a central force (such as gravity in a two-body system), regardless of whether the orbit is circular, elliptical, parabolic, or hyperbolic. Define Angular Momentum L = r x p = m(r x v). Express area of infinitesimal triangle swept in time dt as dA = 0.5 |r x v dt|. Substitute v dt = dr (displacement vector). Relate dA/dt to L/2m by substituting the definition of angular momentum. The force must be a central force (directed along the line joining the bodies). Mass m is constant. Neglects perturbations from other bodies. Thinking the linear orbital speed is constant (speed varies, areal velocity is constant). Believing this law only applies to closed orbits (ellipses) and not open trajectories. Confusing angular momentum L with linear momentum p.