M ) .. Vi MCE wa the Motion of 
? R O ? O S I T I O N I.. 
Let^ fy. g, (tig. l.) reprefent either a cylinder . or that circular- 
fiction of, a body on which it rolls down the inclined plane CA 'in 
confequence ■ of. its frtmon, to find the time, of defcent and the . 
number of revolutions . 
As it has been proved in Art. 5. that the fridibn oFa body:: 
does not increafe in proportion to its weight or preffure, we • 
cannot therefore, by knowing the fridion on any other plane 9 . 
determine the fridion on CA ; the friction therefore on CA can 
only be determined by experiments made upon that plane, that 
is, by letting the body defcend from reft, and obferving the 
fpace deicribed in the firft fecond of time call that Apace a y 
and then,' as by Art. 3.. fridion is a uniformly retarding force 9 
the body muft be uniformly accelerated, and confequently the 
fKc 4 
whole time of defcent in feconds will be = \J~f , Now. to deter-* 
mine the number of revolutions, let s be the center of ofcillation. 
to the point offufpenfion a* ; then,becaufe no force ading at a 
can affed the motion 0/ the point s , that point, notwithstanding 
the adion of the fridion at a, will always have a motion pa- 
rallel to CA uniformly accelerated by a force equal to that 
with which the body would be accelerated if it had no fridion ; 
hence, if zm — 32^ feet, the velocity acquired by the point s 
in the firft fecond will be = ; now the excefs of the ve- 
CA 
. • ’ f 
* « and s are not fixed points in the body, but the former always reprefents 
that point of the tody in contadt with the plane, and the latter the correfponding 
center of ofcillation; 
locity 
