86 ELEMENTARY GENERAL SCIENCE CHAP. 



the centre of gravity ; in unstable equilibrium when a similar 

 movement lowers the centre of gravity, and in neutral equi- 

 librium when the height of the centre of gravity is unaffected 

 by such movement. Consequently, if a body in stable equilibrium 

 is disturbed, it returns to its original position ; if in unstable 

 equilibrium, it will, if disturbed, fall away from its original 

 position ; while if the condition of equilibrium is neutral it will, 

 under similar circumstances stay where it is moved to. 



EXPT. 73. Procure an oblong strip of board or cardboard 

 (Fig. 37). Bore a hole through the oblong near one end, and 

 one through the middle. Support the strip as at A ; it is 

 then in stable equilibrium, for the slightest turn either to 

 right or left raises the cent.ve of gravity. When supported as 



e\ 



FIG. 37. Conditions of Equilibrium. 



at B, the strip is in neutral equilibrium ; and when supported 

 as at C it is in unstable equilibrium. 



A ball resting upon a table is in neutral equilibrium ; for when 

 it rolls the height of the centre of gravity is not changed. 



Conditions of Stability. EXPT. 74. See whether any of 

 the cardboard figures used in the preceding experiments can 

 be hung loosely from a pin with the centre of gravity above 

 the pin. Try the experiment with the pin at different dis- 

 tances from the centre of gravity. In each case notice the 

 direction of the line connecting the centre of gravity with 

 the point of support when the figure comes to rest. 



This experiment illustrates the conditions witli reference to 



