This is the reason why most game physics engine run with a fixed timestamp. You normally set the hz update of your physics engine to either 120hz, 60hz, 30hz. N

This is the reason why most game physics engine run with a fixed timestamp. You normally set the hz update of your physics engine to either 120hz, 60hz, 30hz. Now if your rendering engine is rendering at 120hz and your physics engine is working at 60hz, you can do some very basic interpolation just simply using the objects mass, velocity. Otherwise you run into situation where large deltaV, or very small deltaV completely break the physics calculations. The next is that rounding issue and precision with double still creep in and having a physicist engine that is deterministic for a given hz and float/double speeds up development time.