When a minecart is on a powered track (doesn't matter whether power is being supplied to it or not) and you hit a mob to try and make it go into the minecart, the mob won't go in it but will act as if it has just hit a normal block.
*What I expected to happen was the mob would go into the minecart
*What actually happened was the mob bounced off of it as if it were a building block or fence
Steps to Reproduce:
1. Place a minecart on a powered track
2. Spawn a mob (I used a pig)
3. Try to hit the mob into the minecart (Left mouse-click the mob)
The minecart must be moving if you want a mob to enter it.