I’ve gone skydiving before, and you have maybe 1-2 seconds of that small drop in your stomach feeling before you reach terminal velocity at about 120mph. But that should only make sense if the plane you are jumping out of is going about 90 mph in the vertical direction right? I’m assuming it’s not, maybe flying 90mph in the horizontal axis. So can someone explain why there’s still not a huge change in acceleration to cause that drop in stomach feeling?
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When you exit a plane at 90mph, you will begin accelerating downward at 9.81m/s^2 – but you will also begin accelerating backward at about half that rate, because of the aerodynamic drag on your body. You are losing horizontal velocity as you are gaining vertical velocity in fact, your total acceleration is larger than it would be if the plane was stationary.
But the G force that you feel is a function of the aerodynamic force acting on you, which depends on your speed. You don’t feel the gravitational force because it acts on every part of your body equally – that’s why, if you jump from a static object like a helicopter or hot air balloon, then for the first few seconds you would feel completely weightless, until you gain enough speed to generate significant air resistance.
When you are at terminal velocity, the air resistance is equal to your weight, so it presses up on your body with the same force you would feel if you were lying flat on the ground, so you feel 1G. But when you leave a plane travelling 90mph, the aerodynamic force on your body is about half that, so you’d feel about 0.5G – but you feel it horizontally rather than vertically.
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