Ignorable coordinate
= Ignorable coordinate
A coordinate $q_i$ is ignorable, or cyclic, when $\partial L/\partial q_i=0$. The Euler--Lagrange equation then gives $\dot p_i=0$, so its generalized momentum is conserved.
= Ignorable coordinate
A coordinate $q_i$ is ignorable, or cyclic, when $\partial L/\partial q_i=0$. The Euler--Lagrange equation then gives $\dot p_i=0$, so its generalized momentum is conserved.