114 Domestic Science 



ground. This moment has its point of application at 

 the centre of gravity, and its effect is to cause the 

 lath to be further displaced in the direction of the 

 original displacement. A body is said to be in a position 

 of " unstable equilibrium " when a small displacement 

 of the body from its original position of balance causes 

 further displacement to occur, so that the body takes 

 up a new position with its centre of gravity at a lesser 

 distance from the base of support. 



When the lath is poised about a long narrow face, 

 a small angular displacement may not cause the line 

 of action of its weight to fall without the base of support, 

 and in this case it will be found to return to its original 

 position when the disturbing force is removed. It is 

 then said to be in a fairly stable position. Its position 

 of greatest stability is, however, that in which it is 

 supported on one of its long flat faces. This is the 

 position it always takes up when disturbed from the 

 positions already considered, if the disturbing force be 

 sufficiently great. A body is said to be in " stable 

 equilibrium " when, after a small angular displacement 

 in its position has been effected under the action of 

 a force, it returns to its original position. 



As already illustrated above, there are degrees of 

 stability, and this point may be further examined if 

 we deal with the various positions in which an ordinary 

 brick may be balanced. Its stability increases through- 

 out the series of positions in which it may be balanced 

 given in the following list : 



(a) standing on one corner ; 



(6) . ,, of its shortest edges ; 



(c) longest edges ; 



(d) ,, smallest faces ; 



(e) ,, largest faces. 



