Acceleration v Constant Velocity

This question might seem strange or dumb.. At least it does in my mind, however I phrase it..
Anyway, I'm wondering about the reasons for acceleration being felt and constant velocity not being felt by a human body or other object. If you're sitting in a train or a car and it accelerates rapidly to 100 mph, a bottle might tip over, whereas if you're moving at constant velocity 100 mph, it won't. What exactly is the process by which the energy of that acceleration is felt by any object inside the car or train?

I should note that I don't study physics of any kind, so I won't be familiar with any mathematical formulae that might explain this!

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 Inertia is that "process" (it's not really a process but a fundamental principle of nature). Inertia is the ressistance of objects to some change in their state of motion. That is, if an object is still, it tendes to remain still and if it is moving with constant (in magnitude and direction) velocity, it tends to keep that velocity stable. When you see the bottle going backwards when the train accelerates, that happens because the bottle was moving with a constant velocity which (due to inertial) tends to keep, so when the train accelerates the bottle stays behind. The same principle applies to every object with mass.
 Recognitions: Homework Help Science Advisor As far as we know, physics is the same in all reference frames - there is no "absolute velocity". If you don't look out of the window, you cannot measure the speed relative to the ground (neglecting issues with wheels, sound from the motor and so on). This is a fundemental concept in the theory of special relativity. There are several other motions which would be relevant otherwise: - earth rotates around its center, the surface moves with ~300m/s (depending on your latitude) relative to its center - earth rotates around sun with ~30km/s - the solar system rotates around the galactic center with ~200km/s The train is slow compared to that.

Acceleration v Constant Velocity

So until an amount of energy equal to the object's inertia has influenced that object, it's initial position will be maintained?
For example, if the table on which the bottle is positioned in the train were entirely frictionless, the bottle's position would be completely fixed in space and the table would move forward independent of the bottle?
Or in other words, the reason a bottle tips over in the opposite direction of the train's motion is that the friction between the bottom of the bottle and the table means the lower part of the bottle hangs on to the table while the top half's position wouldn't move if not because it's obviously attached to the bottom half.
Not sure I'm properly communicating what I mean, but hopefully you'll understand..

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 Quote by Fredster1765 So until an amount of energy equal to the object's inertia has influenced that object, it's initial position will be maintained?
That question does not make sense.

 For example, if the table on which the bottle is positioned in the train were entirely frictionless, the bottle's position would be completely fixed in space and the table would move forward independent of the bottle?
It would be fixed relative to the initial motion (for example "fixed relative to the ground"). There is no "fixed in space".

 Or in other words, the reason a bottle tips over in the opposite direction of the train's motion is that the friction between the bottom of the bottle and the table means the lower part of the bottle hangs on to the table while the top half's position wouldn't move if not because it's obviously attached to the bottom half.
"Right"

 About the first quote - I'm probably conceptualizing inertia in an entirely illogical way, but I see it as an object having some quantifiable measure of inertia, or a kind of "negative energy", so the object won't move until it's been influenced by an amount of energy equal to that deficit.. does it make sense? Or am I way off? Right, I wasn't sure how to phrase the 2nd quote, but I mean fixed at some coordinate, or as you say, fixed in relation to the ground. EDIT: I know there's no such thing as "negative energy", but I'm unsure how best to describe what I mean!

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