# Free fall

By Marcus Wilson 08/02/2012

A couple of weeks ago I found this brief article in the newspaper about Vesna Vulovic, who perhaps holds the record for the longest non-fatal fall – a staggering 10 km after a midair explosion on a plane in 1972. I say ‘perhaps’ because the circumstances of the fall are disputed – it is possible that the plane, rather than being at cruising altitude, was attempting an emergency landing and was only 800 m above the ground when it was mistakenly shot down by a Czechoslovak fighter.

Unfortunately Vulovic herself is no help in determining the circumstances since, unsurprisingly considering her considerable injuries, she remembers nothing of the flight.

So the Guinness Book of Records no longer records her feat, and her status as a heroine is in question; so says the article.

Now, hang on a minute shall we? It appears that the  Independent newspaper is suggesting that surviving a fall of 800 metres is a trivial occurrence. I beg to differ on that one. A little bit of physics application would say that surviving the impact from an 800 m fall is every bit as remarkable as surviving the impact of a 10 km fall. Eight hundred metres is not a trivial height – it is plenty of distance for one to obtain ninety-odd percent of  terminal velocity – that is for the force of gravity pulling you downwards to be balanced by the force of air resistance pushing upwards. Once you are at terminal velocity, your impact speed will be the same, whether you fall 1 km, 5 km or 20 km.

There are other factors to consider, however. At 10 km it would be decidedly chilly, especially in Eastern Europe in January. The windchill as you fall at 200 km an hour bear imaging.  Air pressure is much lower, too, meaning that conditions are against you. But in terms of impact alone, there would be no difference.

It’s also worth bringing out the old statistic about cat falls – above a certain height (I forget how much, it’s a few storeys I think) the cats survival rate increases with height fallen because they have longer to prepare themselves for the landing – though I think this statistic and interpretation is disputed. But the point is that above a certain height, and it’s much lower for the pussy cat than it is for the human, the height doesn’t add anything to the impact.