243 
JWOVING FORCE. 
OS _ J OR, it will be obvious, that when N has arrived at Case* of diffi- 
V rulty in the 
S', its velocity will be — , and M will, at the same time, have 
V moving torce. 
arrived at 2', and will have acquired the velocity — , and the 
3 
penetration of C into M will be 4 OR. In this part of the 
operation, then, N has, (on the principles adopted in explaining 
the last case) lost, or rather given out, 1 of its force ; of tl>e 
effects of which are found in the acquired motion of M, and 
^ in the change of figure of M. In the next stage of the ope- 
ration N will have arrived at O' and be at rest : M will have 
V 
arrived at 4‘5, and will have acquired the velocity — . And 
3 
lastly, when M has arrived at 8', it will have acquired the 
velocity j v, and N will have moved back to S", and will have 
V 
re-acquired the velocity — , and the balls will be at the same dis- 
3 
tance they were at first when N struck C. Inexplalning these facts 
by tlie common theory, it is admitted, that N has communicated 
to M a greater quantity of motion than it had j that inconsistency, 
however, is supposed to be removed by saying, that the motion 
of N being in the contrary direction, it must be deducted from 
the motion of M, and the remainder will be equal to the ori- 
ginal motion of N. Bvit we know that a body cannot be put 
in motion, in any direction, without force, and as the final 
motion of N, as well as that of M, must have been derived 
from the original force of N ; it appears that the motion of N 
should be added to, instead of being deducted from, the motion 
of M, before we can properly compare the effects with the 
force by which they have been produced. If N had remained 
at rest at O', M would have been acted upon by C till it arrived 
at 9^ and the whole original force of N would have been found 
in the motion of M, which would finally have acquired the 
I • 
velocity v' 2 * 
This last explanation is given by Dr. Wollaston as follows. 
“ But tliere is one view/’ he obsenes, ** in which the com- 
parative 
