Why exactly does gravity appear stronger when there's an upwards acceleration?
Upwards Acceleration and Gravity
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You don't feel gravity. What you actually feel is the normal force of the floor pushing up on you. If the floor is accelerating you upwards, it will be pushing on you harder than normal, and you will have an increased sensation of weight.
Free-body diagram of the you includes: Force of gravity pulling down (-mg), as well as Fn from the floor pushing up (normally mg). When there is no acceleration, these two forces must be equal. When there is upwards acceleration, the normal force of the floor must be larger than usual in order to provide that acceleration. This larger Fn is perceived as increased weight.
When there is downwards acceleration, Fn must be smaller than usual, because Fg does not change. This smaller Fn would be perceived as decreased weight.
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To include the math:
Ft = Fn + Fg
Fg = -mg this is constant on earth, at least for MCAT purposes
Ft = ma
a = Ft/m
Therefore, if a increases from zero, (moving up), (Fn -mg) must be larger, so Fn must be larger than when v is constant.
If a decreases from zero (moving down), (Fn-mg) must be smaller, so Fn must smaller than when v is constant.
Fn is what you perceive as weight. Therefore, larger Fn = higher perceived weight.
Ft = Fn + Fg
Fg = -mg this is constant on earth, at least for MCAT purposes
Ft = ma
a = Ft/m
Therefore, if a increases from zero, (moving up), (Fn -mg) must be larger, so Fn must be larger than when v is constant.
If a decreases from zero (moving down), (Fn-mg) must be smaller, so Fn must smaller than when v is constant.
Fn is what you perceive as weight. Therefore, larger Fn = higher perceived weight.
