Athletics of To-Day 1929

Athletics of To-day me a great deal more satisfaction when, at forty-two years of age, I beat 150 ft. for fourth place in a country javelin throwing contest than I experienced in winning the first English Championship of rgrr at rr8 ft. and some odd inches seventeen years earlier, simply because I had learned so much more about the event in the years between and felt that the better performance was due solely to a more finished technique. To get this kind of pleasure out of one's sport, however, one must make a close study of the mechanics of throwing. The discus thrower, for example, should understand that from the time the discus leaves his hand until it reaches earth there are, from the mechanical viewpoint, merely two main movements which affect its flight. These are an even balance in the missile FIG. 41 itself, and a perfect parabola of flight. Imagine the discus as an ordinary fly-wheel, such as one may see attached to an engine, uniform in shape and weight and having a true centre, round which centre A the discus revolves at the greatest speed which can be generated by the final spin s imparted by the index finger. The diagram in Fig. 41 represents a discus with centre, C, and ABC a segment of it, while the black portion, AB, represents the outer portion of the segment which rotates around the centre. Any body moving round a centre in a circular path has a tendency to leave that path along the tangent AD, but there is a binding force which reacts to hold the body to its centre. The pull, seeking to drag the defecting segment AB away from its centre, C, and against the binding power working along the lines AC, BC, is called centrifugal force. To stabilize matters and thus obtain a perfect flight the discus must be thrown in such a manner that the centre of gravity will coincide with the centre of rotation. The same considerations do not obtain in the case of throwing the cricket ball or putting the shot. Both missiles are spherical in shape and thus have all points in the circumference equi-