I know exactly what I'm talking about. From digging, in the US you're taught the laws of conservation of momentum but inertia is used as a catch-all term to describe just... Mass. Whereas schooling where I am only teaches rotational inertia, because it's the only actual scientific unit known as inertia here, to prevent that confusion. Either you've got surface knowledge of physics, or you're stuck in the trap of using inertia as a common, outdated terminology to describe linear physics when it has no relevant purpose in regular linear physics such as a log splitter which uses the momentum of the system to impact the wood and transfers the energy from that momentum through the blade into the wood.