We look at the best time to catch, and the best time to leave the bar at the end of a trick.
The Catch
What is perhaps obvious about the position in the swing when the catch takes place is that it must be at a point when both the catcher and the flyer are close enough to touch, this only occurs at the front end. What perhaps is not so obvious is that both the catcher and the flyer must be at the very extremes of their swings.
Let us just consider the fly bar. When the flyer swings, as discussed in Investigation 1, the amount of potential and kinetic energy they have is constantly changing. When the flyer leaves the bar, it is important that they do not move forward (or they will hit the catcher) or back (so they move away from the catcher's hands).
In an ideal catch, the flyer doesn't move horizontally at all, and 'drops' into the catchers waiting hands. This means that the flyer must have no kinetic energy. This occurs when they are at the extreme of their swing. If they leave the bar at this point, they will have no kinetic energy, so they will not be moving forward or backwards. If the catcher is in the same position of their swing, they will both be motionless for a fraction of a second and this is the time for the catch.
A flyer can be caught for a short time either side of this moment, but the catch will not be as smooth. The flyer must be especially careful not to let go before the peak of his swing. If they let go before this stationery point, they will still have some forward momentum, and they will fly forward into the catcher. This will be discussed further in Investigation 8.
In some catches, especially tricks like a Layout that involve a somersault, the flyer may start a movement before the extreme of the swing, but will always let go at the same point, to ensure that while they rotate, they do not travel horizontally.
Dismounting
Dismounting, after a practice swing or a trick not involving a catch, works on a very similar basis to catching. The flyer must ensure that they do not travel either forward or backward. The objective is to land underneath the point where they have let go. Although there is not a catcher to hit if they travel forwards, they could fly into the apron at either end, or the horizontal movement may cause the flyer to lose control and land awkwardly. The correct point to dismount is the same point when the catch would be made, when they have no horizontal movement and no KE. It is important to ensure that all dismounts are carefully controlled like this – landing awkwardly in the net is unpleasant!
Another simple dismount is the back flip. On the forward swing, the flyer swings their legs forwards, then backwards, and forwards again (this just means that the third forward swing has more momentum than a single swing of the legs.) They then let go, and without any extra effort their body rotates backwards and they land on their back. The details of the trick are not important, the take-home message is that although this trick involves a backward rotation, the flyer must again let go at the same moment to ensure that they do not travel forwards.