Mob won't be hit into a minecart whilst minecart is on a powered track

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)