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THE POPULAR SCIENCE MONTHLY 



22 where the arrows FF in the top view represent the forces with which 

 the bearings must act upon the engine shaft to produce the torque T. 



top view 



Fig. 22. 



Gyeostatic Action of a Eolling Disk 



Fig. 23 represents a penny rolling along a floor. The forces FF 



in the side view (the tendency of the penny to fall over) constitute a 



torque which is represented by the arrow T in the top view. This 



torque produces during a short interval of time an increment of spin- 



K Sl t 



top view 



Fig. 23. 



momentum AS which, added to the existing spin-momentum 8, gives 

 the resultant spin-momentum 8' in the direction of which the axis of 

 the penny is found to be turned. The result is that the penny rolls 

 along a circular path as represented by the dotted curve in the top view, 

 Fig. 23. The wheels of a bicycle exhibit a gyros tatic reaction when 



