Sunday, April 27, 2014

On the Boundary Lynn Catch

I am not big on following the Indian Premier League (IPL), but have noticed this fantastic match winning catch that Chris Lynn took to get AB DeVilliers out. If you have not seen it yet here it is on the StarSports website. [If you are in America - here is the YouTube link]

This catch is one of the most athletic ones we have seen in cricket and also he seems to pull off a physics defying jump where he catches the ball and still manages to land within the boundary line. There are certain stills of the catch (like the one above) that would convince you that he had to fall over the line and divine intervention or a extra strong draft of wind is the only thing that made him land well within the boundary limits. This obviously prompted this question on Quora - "Why didn't Chris Lynn fall on the boundary rope while making the best catch in cricketing history?" Here's my answer -

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. Accesses 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.

Thursday, April 10, 2014


Cow fart is essentially a lot of flammable gas (Methane and Hydrogen Sulphide to be precise) coming out of a small hole (The anus to be precise). Any engineer in his right mind will think of only one thing about such a situation. Yes, you are right – Blow torch. So the question is can one hook up some piping to the correct places to build oneself a Bovine Blow torch or a Bove-torch?
First thing is first. We cannot be rude to the cow and set it’s behind on fire. Apart from facing a lot of scorn from animal activist, there is a very high probability of being kicked in the face by a cow on fire.  The revenue generated by this youtube video might make this a good business model, but we will be kind and attach a pipe with a nozzle at the end of it.

 I’ll start with a simple assumption which is probably true (Being from India, unfortunately I have rich experience with being in close proximity to cows) - Cows fart all the time they are awake, continuously. According to this research 13 million cows in USA in 2001 produced 2 million metric tons of Methane which amounts to 160 kg per cow at an average which is 0.0105g/sec. The Enthapy of combustion of Methane is 0.891MJ/mole therefore 0.0105g of Methane produce 584.7J/sec (Watt).

This is only half the story we have some (8.6kg/year) Hydrogen sulphide too being produced which is combustible at 0.519MJ/mole. This is 0.00055g/sec of Hydrogen Sulphide which is 8.8 Watt of energy. OK so this half of the story is not that significant.

Let us assume we are using the blow torch to do some brazing with copper as filler. Assuming 50% efficiency of the torch, the energy required to melt 1g of copper is 509J, in other words - the bove-torch can melt 0.6g of copper every second. You need about 20g of copper to braze a 1 inch diameter pipe joint so you might take about 35-40 seconds to do one which is impressive but not quite blow torch.

Some simple research (read: google) shows that a blow torch must be at least 50,000Watts to cause an American to boast about it. If we hook up say (50000/590 ~= 85) cows to a single tube we might have a proper blow torch that will operate 12 hours a day! So if you have 80 or more cows then you can run a small scale metal blazing / fitting industry at zero operating costs.

More interestingly, these farts also have a LOT of ammonia in there, which is unfortunately not combustible. But if you remember your 10th grade chemistry lesson well and your mind function is evil by nature you will realise that ammonia will combust if you add platinum to the mix as this video will illustrate.

So if we have a platinum nozzle bove-torch (turbove-torch?) things can get really interesting. We have 54.3kg of ammonia per cow per year which boils down to 0.00344g/sec burning with 382.81kJ/mole which is an extra 77.5Watt per cow, that’s a full 15% extra!

May I remind you that you are also contributing to saving the world by doing this as Methane is 50 times more of a green house gas compared to Carbon dioxide.