An electric SUV drove a full loop across a tunnel ceiling at 130 km/h, and the margin for error was 3 to 5 km/h. Slow down by that much at the top and the car falls on its roof. We know because a leaked video of a failed practice run shows exactly that happening. The physics is weirder than the stunt. The critical speed for a vertical loop comes from v² = gr, and mass cancels out of the equation. A five-meter family SUV needs the same entry speed in that tunnel as a supercar would. Extra…