At this point the skater is
has applied a large downward force on the tail causing the board to pop
or bounce off of the ground. The downward force applied is greater than
the force of gravity allowing the board to begin leaving the ground.
During this instant of time the skater has
continued exploding up in t he positive Y direction. In this picture
the
FN is represented by the blue arrow
and the black arrow is the center of mass. The
placement of the front foot before the ollie can determine the overall
height of the trick.
At this point in the ollie the
board and skater have completely left the ground. The instant that the
tail of the board strikes the ground and starts to lift the skater
slides their front foot up the board. The frictional force provided by
the grip tape on the surface of the skateboard and the movement of the
foot up the board is were the major portion of height is gained. The
red arrows indicate the direction of the forces from the sliding of the
foot. The black arrow is the center of mass acting with gravity.