eli5: At constant speed and no vision, are you supposed to be able to tell if you are travelling forward or backwards? How?

Question

Was on the train and it was pitch black outside. Thought I was sitting facing the direction of travel but turned out I wasn’t.

Even when I felt the acceleration/decelerating, I didn’t know which it was.

In: 16

Answer 1

To achieve constant speed you need to balance out the forces going forwards and the forces going backwards, which means there’s no acceleration. This is part of Newton’s first law of motion: every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force. So with no visual aid you wouldn’t be able to tell whether you were stationary or acceleration.