Why I dont really feel any or just little pressure when fly on a plane?

Question

and let say I'm sitting on a rollercoaster and in a car (not convertible) both moving at a speed of 50mph, will i bear more pressure on a rollercoaster than inside a car? i wish my questions are clear. basically i'm asking if the car or a plane will help reduce the pressure i feel, and why.

Answer 1

Planes keep their cabins at a pressure very close to the pressure at the ground, so that the passengers and crew don't pass out. (We can't breathe at those heights!)  So you feel cabin pressure when you fly on a plane -- no more pressure, no less pressure.

Answer 2

Any time you are in a moving reference frame (like a car or a plane or a roller coaster car), you experience a pseudoforce that is equal and opposite the acceleration of the frame.

Note that it is the acceleration, not the speed that matters.  A rollercoaster tends to accelerate a lot to give you a fun ride--up, down, turning.  You shouldn't accelerate nearly that much in a car unless you need to brake rapidly in an emergency or make a sharp turn really fast or like to show off your sports car's power.

In addition to the force, what you feel is the jerk--the change in force.  The roller coaster can jerk quite a bit.  The airplane, on the other hand, revs up its acceleration in a constant manner, so even though the force is substantial, you don't feel jerked by it.