116 



THE STABILITY OF BODIES. 



greater is the work and the greater is the force require* 

 for upsetting it. 



The relation between the stability of a body and its 

 weight, the size of its base, and the position of its centi 

 of gravity, may be briefly expressed by saying that tin 



A / 



FIG. 85. 



stability is proportional to the amount of work that must 

 be done upon the body in order to upset it. 



A few of the simple machines, viz., the wheel and 

 axle, the pulley, are in neutral equilibrium, for they are 

 supported at their centre of gravity. The lever has 

 been used in a position of stable equilibrium, for it wae 

 supported at two points (the extremities of the central 

 hole), situated above the centre of gravity. Being sup- 

 ported in this manner, the lever had only one positior 

 of stable equilibrium, and we were enabled to judg( 

 from a definite position of it, namely, the horizontal, tha 

 it was in equilibrium, and to conclude that there wa; 

 no equilibrium when the lever was inclined. 



The common balance is a straight lever supported ii 

 a position of stable equilibrium. With the help of th | 

 balance we decide whether two bodies (the body t 

 be weighed and the counterpoise) are of equal weigh 

 or not, by ascertaining whether two forces, namely, th 



