Let’s say we have two superheroes standing-off in a weightless environment. Assume that their masses are identical (100kg each). Hero-A gets catapulted at Hero-B – left to right. At the moment of collision, Hero-A’s inertia is transferred to Hero-B, and B hurtles off to the right while A is left behind (stationary) - just as it would in the pool-ball examples (conservation of momentum). Now… instead of bouncing off of each other, let’s say that Hero-A tackles Hero-B and hangs on, effectively DOUBLING his mass at the moment of impact and beyond. If the speed before impact was 100mph, does that mean that the speed is suddenly cut in half at and after impact (because the mass is doubled)?