We human usually anticipate the idea of speed by either visual of relative movement or wind blowing in our face, which is why you might think a car on the highway is still when it is travel at the same speed as yours and why we cannot feel the Earth rotating at a crazy speed when the atmosphere we are in rotates together with us.
In the case of airplane flight, we do not feel the speed since everything is so far from us and move so slowly in our eyes, in turn make us feel like we are moving slow. Trust me, if you fly pass a floating Superman you will be able to tell how fast you are travelling.
It’s important to remember that objects don’t change speed or direction unless something makes them (i.e. a force is applied to the object).
As a vehicle (e.g. a car or plane) accelerates, initially you don’t move at the same speed as the vehicle. Don’t forget – a force has to be applied to you in order to make you speed up. It takes a moment for the speeding up plane seat to apply its forces to you to speed you up.
This is why you feel acceleration – it’s a change of speed and the seat is ‘pushing’ you to go faster and to match the speed of the car.
So, when the car is travelling at a constant speed and when you are travelling at the same speed as the car, you carry on moving at the same speed and in the same direction. No force is needed, so you don’t feel anything.
Probably the most fundamental of all the laws of physics is:
Force = Mass * Acceleration
Acceleration, not speed. So, if you are in a car that accelerates, the seat pushes against your back in order to accelerate you, which you feel as a force on your body. But once you and the car have reached a constant “cruising speed”, and nothing accelerates any more, there are also no longer any forces involved.
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