The Pendulum's Secret

T = 2π√(L / g); frequency f = 1/T. Length L is pivot-to-centre of mass, g is gravitational acceleration. The simple pendulum approximation assumes a point mass, massless rigid string, negligible friction, and small angles. At 25° the actual period is about 1.2% longer. Our animation uses the small-angle cosine solution, not a numerical nonlinear solver. Scene geometry is illustrative, not a metrology instrument.