Licence: In copyright
Credit: Physics for students of medicine. Source: Wellcome Collection.
Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.
39/524 (page 19)
![tliimiest, tliere the tension per sq. cm. of cross-sectional area is fCrcateat ; and there, at the thinnest ]iart, the cord has most tendency to give way and snap. Centrifugal Force.—Suppose a stone to be whirled nnmd, like a slingstone, by means of a string, but in a perfectly circular path. The acceleration towards the Centre is (p. 12) equal to v^-jr, the square of the velocity divided by the radius : the force acting upon the stone, to make it travel in the Circle and not escape along some Tangent, is ■mv-jr dynes, where tn is the mass of the stone, in grammes. In the case of the slingstone this force is exerted by means of the tension of the string : and if t!ie Velocity exceed a certain limit, this tension will l)ecome too great, and the string will snap. The stone will then tiy off at a tangent. A fly will be luirled ofl' a rapidly rotating wheel, for it cannot adhere firmly enough to the rim by means of its feet. The cohesioii of a rapidly rotating wheel may fail, and the wheel fall to pieces, each of which flies off at a tangent. If the earth rotated seventeen times as fast as it does, loose objects would ily oft' its surface at the Equator : their weight would then fail to hold them down. Railway trains tend to fly the track as they come rapidly round curves, and to ruu ofl' at a tangent: the pressure of the flange on the outer rail prevents this. A drop of oil, rotated, spreads out into a flattened spheroid ; and for the same reason the earth is itself an oblate spheroid,' its Polar axis being the shortest. In the trundling of a wet mop the drops fly off. If a man were placed on a revolving table, with his feet towards the centre, the blood in his body would be impelled towards his head ; and this has actually beeii proposeil as treatment for aiiremia of the brain. AVhen light and heavy particles are mixed and whirled th(> heavier fly outwards : thus milk is separate<l by a centrifugal machine from cream, or blood corpuscles from blood plasma Phe circus rtder stands on horse-back slanting inwnrds Hisowii weiglit tends to make him fall inwards: ceutrifiu'ai loree tends to throw him off on the other .side: his actnal position IS one of e(|uilil,rium between these two tendencies. Resolution of a Force.—Where a force acts iu a particular direction, the motion or pressure or tension I'rodueed ill anoUier direction is ascertained by ivsol vim--](https://iiif.wellcomecollection.org/image/b21506516_0039.jp2/full/800%2C/0/default.jpg)
