205 
ite 
: banks == const. 
a 
Te 
r 
This yields the equations 
1 2 2 „2 
r pee r°—p (13) 
a NS “ay 
ee (1-2 Piss 
1 vis ? 
and 
LE AAT Fadia.) AMS Rant Variety 
a 
We will now just express the quantities p and 7 in p‚ 7” and I; 
this is easily done by differentiating (13) and (14) with respect to t. 
The result is 
Pae eee « (15) 
and 
5. From (15) and (16) it follows if r=gp=0 
4 % a a 
g == 0; A 1— — 
2r° r 
This is the acceleration in case of a particle at rest. It is directed 
towards the centre. 
7 has its greatest value (at rest) at the distance 7 = }«@ from the 
centre; the greatest value of d is attained for = 3a. 
6. The motion may be circular. As r is then continually zero, 
we return to the equations (11). The second shows 
au 
eens 
Te: 
: a - 
ea Sai hs? acs Ar 
