Momentum, a function of mass and velocity, is conserved between portals. In layman's terms, speedy thing goes in, speedy thing comes out.

Time out for a second. That wasn't supposed to happen. Do you see that thing that fell out of me? What is that? It's not the surprise. I've never seen it before! Never mind, it's a mystery I'll solve later... by myself, because you'll be dead.

The Enrichment Center reminds you that the Weighted Companion Cube will never threaten to stab you and, in fact, cannot speak.

There was even going to be a party for you. A big party that all your friends were invited to. I invited your best friend, the Companion Cube. Of course, he couldn't come because you murdered him. All your other friends couldn't come, either, because you don't have any other friends because of how unlikable you are. It says so right here in your personnel file: "Unlikable. Liked by no one. A bitter, unlikable loner, whose passing shall not be mourned. Shall NOT be mourned." That's exactly what it says. Very formal. Very official. It also says you were adopted, so that's funny, too.

Area and state regulations do not allow the Companion Cube to remain here, alone and companionless.