system
Given the following post, respond as if you're commenting on Reddit:
human
If travelling in a train close to the speed of light, would you adjust to the speed or would you not be able to move?

I'm having a debate with some friends, they say that eventually you would adjust and basically be able to move freely, as if you were in a normal train that's moving at normal speed.
My hunch is that you would have too much inertia at that speed and would not even be able to move (if somehow you survive arriving at that speed in the first place).
So what is the actual answer to this question?
gpt
Basic physics.  You feel acceleration, not velocity.  

If your acceleration never exceeds 1G, say, in a space ship, you'll feel the same as you do in your living room.  Accelerate faster and you'll feel it more, but when you stop accelerating and stay at a constant velocity you'll feel nothing. 

You can do this in your car. Do you really feel any different when you set the cruise control to 40MPH or 75MPH?    (once you actually reach the desired speed)

Yes, at higher speeds you'll have more inertia, but that inertia will only be noticed by you when you attempt to change the direction of the train/ship. (I strongly advise against attempting a 90 degree turn in a car at 75 MPH)