Moving Force. 231 
machine moving with a uniform velocity (such 
as the float of an undershot water-wheel) the 
maximum effect of moving force will be com- 
municated to the wheel when the part of it 
which is struck moves with half the east 
of the body which strikes it. 
Let A (fig. 17) be a non-elastic soft mass, 
uniforgnly penetrable by the cylinder c, and 
moving in the direction AB with such a velo- 
city v that it would be brought to rest by 
driving the cylinder up to F against an im- 
moveable obstacle—If instead of an immove- 
able obstacle, we suppose B to be the float of 
a water-wheel moving with an uniform velo- 
city =4v, and to be struck by c at F; in 
that case when B has moved through a space 
FH=EF, A will have arrived at G, EG 
being =3 EF, and will have lost half its 
velocity. In this operation 4 of the moving 
force of A has been expended in changing the 
figure of A, 4+ remains with it when moving 
on with the same velocity as B, and the 
remaining 4+ has been expended in pressing B 
through the space FH, and it is easily de- 
monstrable that if the velocity of B be either 
greater or less than $ v, it will be pressed by 
c through a space less than FH. And whether 
A be uniformly penetrable by ¢ or not, the 
same relative velocity of A and B is required 
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