Moving Force, 229 
yeason for taking duration as the general 
measure of moving force, than for taking 
temperature as the general measure of heat. 
It has been shown (page 187) that if a 
given non-elastic body, moving with a given 
velocity, strike an equal non-elastic body at 
rest in free space, half the moving force of 
the striking hody is expended in producing 
change of figure; and in the same manner it 
has been shown (page 197) that, when the 
mass of the striking body is half that of the 
body which is struck, two thirds of the moving 
force of the striking body is expended in 
producing change of figure. 
Upon the same principles, the following 
general theorem is easily made out.—If any 
non-elastic mass A strike another non-elastic 
mass B at rest in free space, (the direction’ of 
the stroke passing through the centres of gra- 
vity of A and B,) the original moving force 
of A will be to that part of it which is 
expended in producing change of figure, as 
A+B: B, and to the remaining moving force 
of A and B after collision, as A+B: A. * 
* The following isa demonstration of this. Let v= the 
oa the velocit 
re a e velocity 
of A and B after collision. The moving force before 
collision will be Av?, and that after collision 
velocity of A before collision; then 
