Page:Popular Science Monthly Volume 78.djvu/199

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195
THE DYNAMICS OF A GOLF BALL

So far I have been considering underspin. Let us now illustrate slicing and pulling; in these cases the ball is spinning about a vertical axis. I must therefore move my electromagnet, and place it so that it produces a vertical magnetic force (Fig. 23). I make the force act

PSM V78 D199 Vertical magnetic force applied to a stream of electrons.png

Fig. 23.

one way, say downwards, and you see the particles curve away to the right, behaving like a sliced ball. I reverse the direction of the force and make it act upwards, and the particles curve away to the left, just like a pulled ball.

By increasing the magnetic force we can get slices and pulls much more exuberant than even the worst we perpetrate on the links.

Though the kinks shown in Fig. 20 have never, as far as I am aware, been observed on a golf links, it is quite easy to produce them if we use very light balls. I have here a ball A made of very thin india-rubber of the kind used for toy balloons, filled with air, and weighing very little more than the air it displaces; on striking this

PSM V78 D199 Ball spinning on its vertical axis caused by an exaggerated slice.png

Fig. 24.Fig. 25.

with the hand, so as to put underspin upon it, you see that it describes a loop, as in Fig. 24.

Striking the ball so as to make it spin about a vertical axis, you see that it moves off with a most exaggerated slice when its nose is moving to the right looking at it from the tee, and with an equally pronounced pull when its nose is moving to the left.