of Central Forces. 407 
gee yy es yy 
ON 
Vi fog age Vier XV? —¥ 
P= 0, Mi =e. 
Hence by taking ns correct fluents there will 
arife 
1—i 
1 hae ied io a 
NE Ea 1—m 
3 é on as Vr —y eee Z = 
: V V lgr 
rr 
, when y= 0, m= 0. 
V dg 
Confequently at the end of any giveh time, 
the place of the body may be found. For, from 
the equations given above, the value of y may 
be found if ¢ be known, and y being known, 
z, or the arc VY will be given. 
» If the time of moving over any given fpace 
in a right line dire@ly from, or tewards the 
centre 
