Put the summary of the bug you're having here
Minecarts can be made to move across land with no rails or propulsion.

*What I expected to happen was...
minecarts, when set up on power rails correctly would move across land for an infinite distance as long as nothing interfears with it.

What actually happened was...:
blocks would be placed either side of powered rails with minecarts on top and when one of the two blocks were destroyed they would move along the ground. I have only tested this on super flat worlds.

Steps to Reproduce:
1. Place 2 building blocks spaced 5 blocks apart.
2. Place powered rails between the blocks.
3. Place down a lever next to the powered rails and turn the lever on.
4. Start placing minecarts on these rails and keep placing them down until no more can fit on the set of tracks. when doing this, the minecarts will move about on the rails and you should stop placing them once the minecarts won't move an more although it is ok to place more down afterwards.
5. simply break 1 of the 2 building blocks and the minecarts will fly off as a group and move along the ground. If this doesn't happen after you've broken the first building block then try the other.