The Physics of Trapeze

Investigation 5: Dismounting

In this investigation, I will 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 performer 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 performer must be at the very extremes of their swings.

Let us just consider the fly bar. When the performer swings, as discussed in Investigation 1, the amount of potential and kinetic energy he has is constantly changing. When the performer leaves the bar, it is important that he does not move forward (or he will hit the catcher) or back (so he moves away from his hands). In an ideal catch, the performer doesn't move horizontally at all, and 'drops' into the catchers waiting hands. This means that the performer must have no kinetic energy. This occurs when he is at the extreme of his swing. If he leaves the bar at this point, he will have no kinetic energy, so he will not be moving forward or backwards. If the catcher is in the same position of his swing, they will both be motionless for a fraction of a second, and this is the time for the catch.

A performer can be caught for a short time either side of this moment, but it will not be as safe (if the performer is moving towards the catcher) and will affect the rhythm. The catch will then not appear smooth, the performers body will appear to jolt in the air, and as he swings down with the catcher, his legs will be swinging awkwardly, dampening the catcher's swing. When the performer moves back to catch the fly bar again, he will have lost energy in the poor swing (just as it is possible to increase energy with a good swing) and will find it more difficult.

In some catches, especially tricks like a layout that involve a flip, the performer may start to flip before the extreme of his swing, but will always let go at the same point, to ensure that while he flips, he does not travel horizontally.

Dismounting - the bullet drop

Dismounting, after a practice swing or a trick not involving a catch, works on a very similar basis to catching. The performer must ensure that he does not travel either forward or back. The objective is to land underneath the point where you let go. Although there is not a catcher to hit if you travel, you could fly into the apron at either end, or the horizontal movement may cause you to flip and you may land awkwardly, perhaps on your neck. The correct point to dismount is the same point when you would make the catch, when you have no KE. It is interesting to note that the most dangerous part of the flying trapeze is not falling, but bouncing out of the net. It is therefore important to ensure that all dismounts are carefully controlled.

A bullet drop is perhaps the simplest of the dismounts. At the extreme of your swing, you push the bar slightly (to give it enough momentum to swing back to the board and be caught for the next person), cross your arms on to your chest, and fall into the net, landing on your back.

Another simple dismount is the back flip. On the forward swing, the performer 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 flips and they land on their back. Although this trick involves a flip, the performer must again let go at the same moment to ensure that they do not travel.

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