Hello. I've been watching Susskind's online Stanford lectures on classical mechanics to review the subject, and I believe he said that adding a constant to the potential energy does not change the action of a system. I see how it doesn't change the Euler-Lagrange equations and therefore doesn't affect the equations of motion (and therefore the trajectories), yet the integral of a constant is non-zero so I don't see how adding a constant to U in A = ∫(T-U)dt wouldn't change the action A. Where have I gone wrong? There seems to be an inconsistency in saying that the action changes (implying it's not at a minimum and therefore doesn't describe the true trajectory) while the E-L equations don't change (implying no change in trajectory). Thank you, sorry if I'm missing something basic and have wasted your time by not thinking about this more on my own :)(adsbygoogle = window.adsbygoogle || []).push({});

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# I Adding a constant to potential energy doesn't change action?

Have something to add?

Draft saved
Draft deleted

**Physics Forums | Science Articles, Homework Help, Discussion**