X. 



FRICT1O*. 



KI Is the investigations of the preceding Chapter, we 



have supposed that the surface* of the bodies <-t are 



I'.y a smooth surface is meant a surface 



I>osc8 no resistance whatever to th ->f a body 



surface which does oppose a resists n 

 :' a bodj upon it is said to be rough. In prnrv it is 

 1 that all bodies are more or less rough. 



lion of | >n a surface is measured by the 



least force which will put the body in m-.tion along the 



Mirtao'. 



>ul>inl> made a aeries of < nts upon the fric- 



k dies against each other and deduced the following 

 laws. Mf moires des Savans Etrangtrs, Tom . x . 



(1) The friction varies at the normal pressure when the 

 lab of the surfaces in contact rem \\Tien 

 ressores are very great indeed, it is found that the fric- 

 ;H somewhat less than this law would L- 



(2) u independent of the extent of tlr surface* 

 t/i contact so long as the normal pressure remains the same. 



Wli.-n tin- -urlacrs in contact a all, as for in- 



stance a < resting on a surface. aw gives the 



much too great 



*e two laws are true when the body is on the point of 

 Mg and n n it is actunlly i: ; hut r 



case : in.iirni tude of th 



same as v. body is in a state bonl* <ion : 



ro is a difference tin- t'rirti<>n is greater in i:.*- state 

 bordering on moti ; actual motion. 



(3) The friction is independent of the vtloctty when the My 



