- This is the situation provided where it has to be demonstrated that linear momentum is not conserved or unrealistic. My assumptions are: there's no friction due to how Godzilla is moving, the sand is acting as a lubricant. Velocity is constant. This is an elastic collision. I also guess that we have to calculate the force that Godzilla applies on the two masses combined (Megalon and Jet Jaguar) in order to prove that the force required for Godzilla to push both Megalon and Jet Jaguar is unrealistic.

My problem is, I don't really know how to calculate the force that Godzilla applies on both masses. And if that's not what's need to calculate, then I really don't have an idea of what to calculate to prove linear momentum is not conserved/unrealistic.

If I understand properly, you want to demonstrate that what happens in the video clip is impossible because it implies a violation of conservation of momentum? Is this a homework/ coursework question?

You should be able to make a reasonable estimate of the total momentum before and after the collision from reasonable estimates of the mass of the participants and their before and after speeds.

Science fiction like this rarely cares about conservation of momentum. The authors simply ignore it. In this particular case I don't see an obvious violation of it. The sliding approach looks really unrealistic, however.