144 



CENTRIFUGAL FORCE 



CH. IX 



will be exactly balanced by that of the weight, 

 or else the bicycle will fall to one side or the 

 other. 



In Fig. 72, where the man is turning to the left, 

 the centrifugal force will be developed in the direc- 

 tion indicated by the arrowhead, and may be repre- 

 sented by the line CF ; the weight acting vertically 

 downward is represented by C\V. The resultant 

 of these two forces will be represented in amount 



by CB in the direction of the 

 line CD, and the point of sup- 

 port must be in this line, as at 

 D, to prevent the man from fall- 

 ing. II the speed, and conse- 

 quently the inclination, is not 

 great, the bicycle may go safely 

 round a level curve, but if the 

 speed be greatly increased the 

 wheel may slip on the ground. 

 To avoid this, the surface must be sloped, as shown 

 by the dotted line, until it is at right angles to the 

 inclination of the rider. 



This is done in a circus ring by heaping the earth 

 at the outer edge, and in a cycling track by sloping 

 the asphalt path on the curve, at angles propor- 

 tional to the squares of the speeds, one part of the 

 curve, usually the lower, having steeper slopes than 

 the upper, to suit all speeds. 



The inclinations of the line CD, and consequently 

 that of the lines at right angles to it, will be propor- 



Fig. 72. 



