I agree that accidents can be prevented. But you said its not an accident if someone trips over an electrical cord left on the stairs. So moving the cord would prevent someone tripping but, by your logic it would not have prevented an accident.
I would say someone tripping over a cord that someone else did not move is an accident. You do not agree: “An accident is something that could not be prevented.”
But despite saying that you go on to call the trip an accident “If you see a coiled up electric cord on the stairs you should move it because it might cause an accident if somebody else trips over it.”
“If you don’t move it and somebody trips and gets hurt it wasn’t an accident because it could have been prevented by the person not leaving it there or you when you noticed.”
So is the tripping an accident or not?
No!
If something can be prevented and you don’t prevent it then it is not an accident.
If you let your kids play in a busy street and they get hit by a car it wasn’t an accident - it’s your fault because you let them play in a busy street.
If you let them play on a quiet side street with a 20mph speed limit and a dude come ripping around a corner squealing tires and hits one of them - that wasn’t an accident either. But it was the fault of the speeder.
If you’re tearing down an old building and pull off a board with nails in it and you drop it on the ground nails up and somebody steps on it and punctures their foot it was not an accident because you caused it when you could have prevented it.
There are real accidents but most “accidents” could have been prevented. So tripping on the stairs would seem like an accident to the one who tripped - but it was caused by the lazy person who didn’t move the cord.
Be aware of what you are doing, notice what’s around you and there will be fewer “accidents” around you.