## 06 August 2012

### Tuesday Preview #1: Men's Discus

My pre-Olympics pick to win the men's discus throw was Robert Harting of Germany.  He's in good shape after coming in second in the qualifying round with a throw of 66.22 m (217.3 feet), just behind the 66.39 m (217.8 feet) thrown by Gerd Kanter of Estonia.  The world record for men's discus throw was set in 1986 by Jürgen Schult of Germany at 74.08 m (243.0 feet), which is the longest standing world record for men's outdoor track and field events (click here for the list).  Harting and Kanter will need to increase their throw distances by almost 12% to match Schult's 26-year-old record.

So, what do Harting, Kanter, and the rest of the field need to do to match Schult?  The discus fascinates me enough that I devoted an entire chapter to the event in my book.  My focus in that chapter was on the great Al Oerter, who won discus gold in four straight Olympics (1956, 1960, 1964, and 1968).  Consider the graph below (click on the image for a larger view).
The above graph appears in my discus chapter.  The angle on the horizontal axis is the launch angle, which is measured with respect to the ground.  The angle on the vertical axis is the discus inclination, which is the angle between the long axis of the discus and the ground.  The launch speed for all throws in the above graph is 25 m/s (90 km/hr or 56 mph).  The three "islands" represent all possible values of the two angles that allow the discus to land within 1 m (3 feet) of the range given in the middle of the island.  The top island has a tailwind of 10 m/s (36 km/hr or 22 mph); the middle island has no wind; the bottom island has a headwind of 10 m/s.

Wait, can that be right?  The discus can be thrown farther with a headwind than with a tailwind? It turns out that a tailwind hurts the lift force on the discuss because the air speed is not as great over the discuss as with a headwind.  A headwind allows the discus to act like a sail and stay in the air longer.  Too much headwind, though, increases the drag enough that added lift won't matter.  Note that the world record is sitting in that bottom island, which has the smallest room for error to get the discus to within 1 m of the record.  What Harting and Kanter have done so far in London is essentially in the middle island (assuming they had no wind on their throws).

Harting, Kanter, et al will need a little help from the wind and phenomenal technique if they want to match Schult's record.  Harting has thrown just over 70 m in his career, but reaching Schult will be tough.  I'll still go with Harting for gold on Tuesday.