I'm wondering if it is forbidden to go onto a moving train on shabbos.
I'm having a hard time understanding the answer I heard before: the extra weight causes the train to use more power.
I thought about that answer for a while, and I realized that it would be such a small amount of work being done it must be nullified.
So, is it forbidden to go onto a moving train on Shabbos? If so, why?
EDIT: the case I have in mind here is not related to that if a subway. With the case of a subway, there's the issue of paying etc.. I'm simply wondering about why the added weight you cause by jumping onto a slow moving (freight) train (let's say, to not confuse this with a subway case) is forbidden on shabbat.