Sir Isaac Newton based his mechanics on vector quantities like forces and acceleration. This approach requires tracking the direction and magnitude of every force acting on a system. For systems with constraints—like a pendulum confined to a circular arc—calculating these forces becomes tedious.
𝜕L𝜕ẋ=(m1+m2)ẋ⟹ddt(𝜕L𝜕ẋ)=(m1+m2)ẍthe fraction with numerator partial cap L and denominator partial x dot end-fraction equals open paren m sub 1 plus m sub 2 close paren x dot ⟹ d over d t end-fraction open paren the fraction with numerator partial cap L and denominator partial x dot end-fraction close paren equals open paren m sub 1 plus m sub 2 close paren x double dot lagrangian mechanics problems and solutions pdf