THE GYROCAR 



set spinning, and the outer frames will remain stationary 

 unless a disturbing force is applied to them. 



Suppose, now, that the wheel has been set spinning on 

 its axis O ^ in the direction indicated by the arrow, 

 while its axis is horizontal, as represented in the diagram. 

 The wheel will then tend to maintain its position 

 and resist any attempt to displace it. But its resistance 

 will be shown in a very peculiar way — whereby hangs 

 our tale. If you apply a steady downward pressure to 

 the frame B A C ^t point A, attempting thus to deflect 

 the axis of the spinning wheel of the gyroscope, the 

 frame will not tip down as you expect it to do (and as 

 it would do if the top were not spinning) but instead, it 

 will move in a horizontal plane along the arc CAB, 

 the entire mechanism rotating on the axis D E. This 

 motion is equivalent to the wabble of the top, and it is 

 called "precession." 



Please remember the word and its meaning, for we 

 must use it repeatedly. 



But now, curiously enough, if you were to apply a 

 sidewise pressure at A, pushing to the left (as we view 

 the diagram) to help on the motion of precession, the 

 obstinate apparatus will cease altogether to move in that 

 direction and the point A will begin to rise instead, the 

 frame B A C rotating on its axis B C This rise of the 

 axis O A will take place even though the downward 

 pressure is continued. You have disturbed the equilib- 

 rium of the top — unbalanced it — ^and it must seek a 

 new position. Contrariwise, if you would have the point 

 A moved to the right, you must push it upward ; if you 

 would have it go down, you must push it to the right. 



[«>5] 



