FORCE AND MOTION. 33 



of matter bo move in a straight line, and, conse- 

 quently, further away from the centre around 

 which it is revolving, is called Centrifugal Force, 

 from the Latin words which mean to fly from the centre. 

 The "laws" of this "centrifugal force" may be studied 

 or illustrated by the whirling-table and accompanying 

 apparatus, represented in Figure 7. (See 77.) 



75. Caution. It is to be noticed that this so-called 

 " Centrifugal Force " is not a force at all. It is 

 simply inertia manifested under special conditions. It is 

 one of the universal properties of matter by virtue of 

 which the body shows a decided determination to obey 

 the first law of motion. The facts of the case are the 

 direct opposite of those implied by this ill-chosen name. 

 Take a common sling, for instance. The implication made 

 by the term, " Centrifugal Force," is that the pebble in the 

 revolving sling has a natural tendency to continue moving 

 in a circle, and that some external force is necessary to 

 overcome that tendency. The truth is that the natural 

 tendency of the pebble is to move in a straight line, and the 

 o"nly reason that it does not thus move is that it is continu- 

 ally forced from its natural path by the pull of the string. 

 As soon as this external force is removed, by intent or 

 accident, away flies the stone in obedience to its own law- 

 abiding tendencies. 



76. Simply Suggestive. Examples and effects of 

 this so-called centrifugal force may be suggested as follows: 

 Wagon turning a corner, railway curves, water flying from 

 a revolving grindstone, broken fly-wheels, spheroidal form 

 of the earth, erosion of river-beds, a pail of water whirled 

 in a vertical circle, the inward leaning of the circus-horse 

 and rider, the centrifugal drying apparatus of the laundry 



