The answer to this question lies in Newton's Three
Laws of Motion (
read here ).
For this, we employ Law 1 and Law 3:
Law #1: An object at rest stays at rest
and an object in motion stays in motion unless
acted on by an outside force.
Law #3: Every action has an equal and
Let's say you're jumping out a window and want to
veer left. For this to happen, by Law #1, an
outside force must push or pull you to the left.
In this scenario the only force source you have to
play with are your flailing limbs.
Unfortunately by Law #3, any force exerted by
a twist or a limb flail has an equal and opposite
force by the rest of your body that will bring
your trajectory back to the direction you started.
Hence, your net force will always be zero. A fun
and less-lethal way to test this out is to find a
swivel chair with very little friction, lift your
legs off the ground and try to twist and flail
your body to rotate either clockwise or
counterclockwise. What you will find is that no
matter how fast or twisty you move, you will
always end up stationary where you started. (You
may experience some displacement due to friction)
Please note, everything said above only
works in a vacuum and does not take into account
the fluid mechanics of the air. Accounting for
air pressure, you can DEFINITELY change trajectory
mid jump. Skydivers can twist their hands and
bodies to move from side to side and rotate. Also
birds are very adept at changing trajectory while
"jumping" off of things! The "outside
force" in this case comes from differences in
air pressure, because pressure is a force over an