Why didn’t Chris Lynn fall on the boundary rope while making the best catch in cricketing history?

In case you were wondering…
Also, would make for a very interesting exam question…

Answer by Mahek Mody:

Let's start with a slight detour – There is a very famous (& I think very cool) physics fact about pole vault. When a pole vaulter jumps a high bar, her Center of Gravity (CG) need not go as high as the bar she needs to clear. In other words, at the top of the jump the pole vaulter needs to go over the bar and not her CG. To achieve this the pole vaulter arches her back forwards or backwards to be in a situation where the body is clear of the bar but the CG passes under for the most optimal jump. The idea being that Newton's laws only dictate the trajectories of the CG and not the entire body.

Lynn's miraculous falling back within the boundary rope is something similar. After the little stumble he has just before he makes his jump, he has his eyes on the ball. Assess the trajectory of the ball, and it looks something like this –

Now Lynn considers jumping straight up and try get the ball. Is there a chance he can make it? His jumping ability is limited and there is only a limit to which he can raise his CG. He would not have caught the ball.

However, if he jumped and turned back at the same time things could look very different even if the his jumping ability is considered to be the same. As this diagram illustrates –

At this point if a snap was taken it seems as if he would fall on the boundary rope, but he has some angular (spin) momentum on his side which a still would not capture.

He does exactly that makes the catch and after which since his CG is still very much inside the boundary region he can easily use his flexible and agile body to bring his hands inside the boundary rope. Eventually using his hands to safely land well within the boundary.

I am sure Lynn did not go through all this physics in his mind before making the catch, but intuition is a powerful physics engine due to the world experience it has.

Cross posted on my blog – On the Boundary Lynn Catch

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