CH. IX CENTRE OF GRAVITY 1 37 



elevation of the wheel very much less than that 

 required to make the coach balance, will result in 

 an overturn.* 



Since the whole weight of the coach may be con- 

 sidered as concentrated at the centre of gravity, 

 any sideways force, resulting from the momentum 

 of the coach, will act through that centre. 



If, from going fast over a bad road or from the 

 horses galloping unevenly, a coach gets to swinging 

 laterally, the higher the centre of 

 gravity, the more readily will the A *~ 

 coach turn over, since it is obvious B * \\_ 

 that a horizontal force applied to 



the coach near the top (as at A, ////////V//////^//////, 



Fig. 68) will pull it over more FlG - 68 - 



readily than the same force applied nearer to the 

 ground (as at B). 



Centrifugal Force. — The danger in turning a 

 corner is increased by a high centre of gravity. 

 A body in motion has, by reason of its inertia, a 

 tendency to continue its motion in the original di- 

 rection until it is acted upon by some exterior force. 

 A coach going along a straight road is deflected, 

 when it comes to a corner, by the horses pulling 



* Corbett, p. 26, quotes some experiments made by Vidler in 

 1820, in which it is stated that in the case of a mail, the wheel was 

 raised 26 inches without an upset, and in the case of a ' double 

 bodied coach,' 31 inches, but he does not say whether this was 

 exactly the point of balance, or not. 



