Parabolic motion is a term that describes the motion of the footbag through the air. Often the bag is described only as moving up and down, which is just for the sake of simplicity.
Parabolic motion with uptime, midtime, and downtime components illustrated.Parabolic motion as applied to footbag freestyle is essentially simply the natural gravitational effect of setting the footbag up with a certain amount of force and at a certain angle (which affects the width of the parabola) which determines the height and ultimate landing place of the footbag. (See [1] for more information on parabolas in general.)
Not only does the bag move towards, away, to the left, and to right (perspectively) of the player, the player will often set the bag into a parabolic motion that allows him/her to hit the trick more easily.
Parabolic motion can be easily noticed in consecutive far butterflies, which are also called infinities, because the motion of the bag is in that of an infinity symbol.
Parabolic motion with uptime, midtime, and downtime components illustrated.Parabolic motion as applied to footbag freestyle is essentially simply the natural gravitational effect of setting the footbag up with a certain amount of force and at a certain angle (which affects the width of the parabola) which determines the height and ultimate landing place of the footbag. (See [1] for more information on parabolas in general.)
Not only does the bag move towards, away, to the left, and to right (perspectively) of the player, the player will often set the bag into a parabolic motion that allows him/her to hit the trick more easily.
Parabolic motion can be easily noticed in consecutive far butterflies, which are also called infinities, because the motion of the bag is in that of an infinity symbol.
It is important to note that the vast majority of top players try their hardest to set the bag exactly straight up and down, with no sideways motion at all (thus, an imperceptibly narrow parabola). 5-time world champion Vasek Klouda is a fantastic example of not setting the footbag sideways. Some players view wider parabolic sets as "sloppy" or "unclean".
Either way, the parabolic motion (however narrow the parabola) is the foundation of freestyle move analysis as we define move components using the basic chart on the right.
A projectile is an object upon which the only force is gravity. Gravity, being a downward force, causes a projectile to accelerate in the downward direction. The force of gravity could never alter the horizontal velocity of an object since perpendicular components of motion are independent of each other. A vertical force does not effect a horizontal motion. The result of a vertical force acting upon a horizontally moving object is to cause the object to deviate from its otherwise linear path. This is depicted in the animation below
According to Newton's law of inertia, an object in motion in a horizontal direction would continue in its horizontal motion with the same horizontal speed and direction unless acted upon by an unbalanced horizontal force. The animation above shows a green sphere moving to the right at constant speed. The horizontal distance traveled in each second is a constant value. The red sphere undergoes a vertically accelerated motion which is typical of an object upon which only the force of gravity acts. If these two motions are combined - vertical free fall motion and constant horizontal motion - then the trajectory will be that of a parabola. An object which begins with an initial horizontal velocity and is acted upon only by the force of gravity will follow the path of the blue sphere. It will travel the same horizontal distance in each consecutive second but will fall vertically a greater distance in each consecutive second. The result is a parabolic path as shown in the animation above.
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