54 MOTION AND FORCE 



support taken in order. Fig. 37 shows eight points 

 of support; the base is the area bounded by dotted 





FIG. 37 FIG. 38 



lines. In Fig. 38 dotted lines show the base of a person 

 standing. 



A pencil supported as at c (Fig. 39) would be said to 

 be in a state of equilibrium; that is, the force of gravity 

 acting on ac is just balanced by that acting on be. If 

 Q b c were moved a little, 



GL^=^^^ aa ^ miSllxailsa ^ ailliiliis _ m -^^^\ ^^ 



these forces would no 

 FlG - 39 longer balance, and 



the pencil would fall in the direction of the greater 

 force. 



64. Stability. A body which is less easily tipped 

 over than another is said to be more stable. In general, 

 the lower the center of gravity or the broader its base, the 

 more stable a body will be. 



Experiment 48. Stand your pencil on its end ; then lay it on 

 its side. In which position has it the broader base ? In which is 

 it the more stable ? 



Experiment 49. Pile up three books and test the stability of 

 the pile. Then add as many more as you can, and test that. 

 Which pile is the more stable? Why? 



Try to balance your ruler, first on its side and then on its end. 

 Which is easier, and why ? 



