
Originally Posted by
Gredival
Troll physics... sort of.
When you travel with a moving object, you acquire the directional velocity of that object. If you were in a truck flatbed passing under a bridge and you hurled a basketball straight up in the air, it would travel in an arc, not just go up and down, because it has forward velocity from the truck and not simply upwards velocity from your toss. It's like the scene in Spiderman 1 where Peter jumps over a bridge by simply jumping straight up in the air on a moving train.
Similarly when you are hurtling downwards, on a chair or a plank or whatever, you are acquiring your own independent velocity. What kills you is the force with which you hit the ground (which is effected by speed) and the rigidity of the ground that redirects that force into your body. Now you could theoretically slow yourself by jumping upwards, however with how tall skyscrapers are, it would be impossible for a normal person to generate enough lift to substantially reduce the force of impact to survivable levels. Not to mention that you need to attach yourself to the chair in some way to have the contact necessary to jump off from it, and I foresee difficulty in doing that