Success in Athletics and how to obtain it

DISCUS-THROWING but it is held and pulled to that centre by some binding force, whatever it may be, along a c and b c. This pull or push, tending to move the defect– ing segment away from the centre, is called "Centri– fugal Force." To obtain perfect rotation, the "centre of gravity " of the body must coincide with the "centre of rotation." Now, in the case of a cricket-ball, it will be readily understood that all points on its circumference are equidistant from its centre of gravity, and that when it is throwq into the air it does not matter how much it rotates or skims, it will always be travelling with an even centre, and consequently there will be nothing which will tend to make it eccentric in its movements. But not so with a discus. Diagram z6 shows a section, or cut, through the centre of the discus. The black dot represents its j .. ~ ~ Diagram 26. centre of gravity, round which it will r-9tate, when it has been given the necessary twist. Now, pro– vided it is rotating fast enough and has been returned truly, it will travel through the air "flat"; but should it revolve slower whilst on its journey it will wobble, or, in other words, it will commence to change its rate of rotation, which was previously only maintained by the speed of its revolution. round its centre of gravity. Diagram 27 will probably give some idea of what actually takes place, and how the discus rotates verti– cally after its horizontal rotation has become practi– cally nil.