MECHANICAL PARADOXES. 



horizontal axis, it may be supported, as we 

 have seen, at one side of the axis only, either 

 in our original simple experiment with a string, 

 or in a well-made gyroscope by placing the 

 knob at one side of the frame in a cup-shaped 

 hollow on the top of a small pillar-stand. 

 When it is in this position the force of gravity, 

 in trying to pull it down, necessarily tends to 

 give it a twist. Since one end is supported, 

 the spinner as a whole can only come down 

 by the dropping of the unsupported end, 

 which involves a twisting of the spinner so 

 that one face would look more downward and 

 the other more upward. 



Such a twisting its spin enables it, as we 

 have seen, to resist with considerable force, 

 so that rather than be twisted it can remain 

 with its axis horizontal, though supported only 

 at one end. 



We must now turn to the question : How 

 does its spin enable the gyroscope to maintain 

 its position against gravity ? 



To begin with, it does not quite do so. It 

 only comes so near doing it that, unless we 

 look closely, we do not notice the slight failure 

 to keep truly horizontal, which, however, goes 

 on increasing, and the more rapidly as the spin 

 gets slower. 



What we have to account for, then, is 

 simply a strong tendency to keep the axis 

 horizontal. 



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