of Central Forces. 413 
aa 7 . 
cafe at prefent, == — —; therefore the centri- 
- y - 
i } =? 3? Fs 
petal force = —- F — = — 
a J 
n-}-s 
fuppofe, to 4 
en 
Multiply both fides of the 
equation by y, and take the fluents, then + x 
*2 Arr 2 
ON i meg te But xiy:: bse, Of as 
oe mu—l1 x b i tacs x 
2 c ; 
= when y==r, therefore the fluents cor- | 
2 5? a n—f-1 
rected become “ —— x E he 
x 
nu—lI 
bao sy rn? 
, ae eras 
™—1 
b V n—1 x r—. — ¥ 
; which gives 
= ——_—_—_————————— 
Pa 17 —2 Art kaa -+ 2 At pr 
But in Prop. I. it was found, that if a body 
defcended from an infinite height, and was 
nts r 
acted upon by a force = a, the fquare of 
the velocity acquired at the diftance r was = 
Q Arts 2m Ant 
: ; let therefore —— 
n—1 XK pet! n—1>*K pr! 
—~—.€y 
—— 
—_—_—-- 
