火車如何出軌?火車為什麼出軌?

For every object to travel in a circular path, there must requires a centripetal force. In the case of a train, the centripetal force is provided by the rails onto the wheels.
Thus, centripetal force F = mv^2/R
where m is the mass of the train
v is the speed of the train
R is the radius of the circular path where the train turns.
The max force F provided by the rails onto the wheels is more or less constant, thus when v is high enough such that
mv^2/R > F
the centripetal force F is not sufficient to drive the train to turn the corner, then derailing of the train will occur.

1 人為破壞導致火車出軌可能興很高

2 鐵軌膨脹也有導致