Momentum is not conserved with elastic bouncing ball?

[vizakenjack]

So if you throw an elastic bouncy ball at the non-closed door, it will bounce off with bigger velocity than it was approaching the door before hitting it, as well as the door will now have some gained momentum and will move.

P (momentum) = mv

In this case, it appears as if the ball gained additional momentum (after hitting the door) out of nowhere...

In fact, if you compare it to throwing an inelastic ball at the door, then the inelastic ball after hitting the door will give all of its momentum to the door and then simply fall down to the ground.

I also read this thread already.

 

[WarDieS]

Unless the door is moving against the ball, the ball won't bounce with more velocity.

Momentum is always conserved

 

[A.T.]

So if you throw an elastic bouncy ball at the non-closed door, it will bounce off with bigger velocity than it was approaching the door before hitting it

Where have you seen that?