i84 TEE POPULAR SCIENCE MONTHLY 



THE DYNAMICS OF A GOLF BALL^ 



BY Sib J. J. THOMSON 



CATBNDISB PEOFBSSOB OF EXPERIMENTAL PHYSICS, DNIVBBSITY OP CAMBBIDGB, 

 FBOFESSOR OF NATUBAL PHILOSOPHY, BOYAL INSTITUTION 



THERE are so many dynamical problems connected with golf that a 

 discussion of the whole of them would occupy far more time than 

 is at my disposal this evening. I shall not attempt to deal with the 

 many important questions which arise when we consider the impact 

 of the club with the ball, but confine myself to the consideration of 

 the flight of the ball after it has left the club. This problem is in 

 any case a very interesting one, it would be even more interesting if 

 we could accept the explanations of the behavior of the ball given by 

 many contributors to the very voluminous literature which has col- 

 lected round the game; if these were correct, I should have to bring 

 before you this evening a new dynamics, and announce that matter 

 when made up into golf balls obeys laws of an entirely different char- 

 acter from those governing its action when in any other condition. 



If we could send off the ball from the club, as we might from a 

 catapult, without spin, its behavior would be regular, but uninterest- 

 ing; in the absence of wind its path would keep in a vertical plane, 

 it would not deviate either to the right or to the left, and would fall 

 to the ground after a comparatively short carry. 



But a golf ball when it leaves the club is only in rare cases de- 

 void of spin, and it is spin which gives the interest, variety and 

 vivacity to the flight of the ball. It is spin which accounts for the 

 behavior of a sliced or pulled ball, it is spin which makes the ball 

 soar or " douk," or execute those wild flourishes which give the im- 

 pression that the ball is endowed with an artistic temperament, and 

 performs these eccentricities as an acrobat might throw in an extra 

 somersault or two for the fun of the thing. This view, however, 

 gives an entirely wrong impression of the temperament of a golf ball, 

 which is in reality the most prosaic of things, knowing while in the air 

 only one rule of conduct, which it obeys with unintelligent conscien- 

 tiousness, that of always following its nose. This rule is the key to 

 the behavior of all balls when in the air, whether they are golf balls, 

 base balls, cricket balls or tennis balls. Let us, before entering into 

 the reason for this rule, trace out some of its consequences. By the 

 nose of the ball we mean the point on the ball furthest in front. 



* A lecture given before the Royal Institution of Great Britain. 



