Law Of Conservation Of Mechanical Energy — the NEET Physics formula with its derivation, variables, validity constraints and worked solver.
Law of Conservation of Mechanical Energy Valid only in closed systems involving conservative forces (specifically gravity in this form) with no non-conservative work done (friction, air resistance). Start with the Work-Energy Theorem: W net = Delta K. Define Work done by conservative gravity as W g = -Delta U. Assume no non-conservative forces: W net = W g. Substitute: -Delta U = Delta K. Rearrange: Delta K + Delta U = 0, implying K i + U i = K f + U f. Mass must be constant. No external work added or removed. Velocities are non-relativistic. Believing mass affects the final velocity in free fall (mass often cancels out). Applying the law when friction or drag is present. Confusing height relative to the ground versus height relative to a reference point. Thinking potential energy is absolute rather than relative to a chosen datum.