Life and Scientific Work of Peter Guthrie Tait - School of Mathematics ...

THE PHYSICS OF GOLF 27
experimentally by Magnus in 1852 but already made clear by Newton in
1666, that, when a spherical ball is rotating and at the same time advancing
in still air, it will deviate from a straight path in the same direction as that in
which the front side is being carried by the rotation. Thus (to quote Tait)
" in topping, the upper part of the ball is made to move forward faster than
does the centre, consequently
the front of the ball descends in virtue of the
rotation, and the ball itself skews in that direction. When a ball is undercut
it gets the opposite spin to the last, and, in consequence, it tends to deviate
upwards instead of downwards. The upward tendency often makes the path
of a ball (for a part of its course) concave upwards in spite of the effects of
but
gravity...."
This last sentence contains the germ of the whole ; explanation
it
was not developed by Tait till four or five years later. Neither here nor in
any of his writings on the subject is any rash statement made as to the greatest
possible distance attainable by a well-driven golf ball. In his first article " On
the Physics of Golf" {Nature, Vol. XLii, August 28, 1890) Tait calculates by an
approximate formula the range of flight of a golf ball for a particular elevation
and various speeds of projection, the ball being assumed to have no rotation.
In this way by comparison with known lengths of "carry" he finds a probable
value for the initial speed of projection. He also points out that, to double
the " carry," the ball because of atmospheric resistance must set out with nearly
quadruple energy. About a year later (Sept. 24, 1891, Nature, Vol. XLiv,
p. 497), he treats more particularly of the time of flight. He finds that,
although we may approximate to the observed value of the range
of a well-
driven ball by proper assumptions as to speed and elevation, it is impossible,
along those lines, to arrive at anything like the time of flight. The non-rotating
golf ball will according to calculation remain in the air a little more than half
" The only way of
the time the ball is known from experience to do.
reconciling
the results of calculation with the observed data is to assume that
for some reason the effects of gravity are at least partially counteracted.
This, in still air, can only be a rotation due to undercutting."
Thus he comes back to the rotation of the ball as the feature which not
only explains the faults of slicing, pulling and topping, but is the great secret
of long driving. When the rotation is properly applied as an underspin about
a truly horizontal axis, the ball goes unswervingly towards its goal ; but, when
owing to faulty striking the axis of rotation is tilted from the horizontal one
way or the other, there is a component spin about a vertical axis and the ball
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