66 
Caies of diffi- 
culty in the 
doctrines of 
moving force. 
MOVING FORCE. 
and if F H and F I be taken each = ^ E F, when the side of 
A has arrived opposite to H, the side of B will have arrived -i 
opposite to I, (as represented at No, 2.) and the velocity of 
both balls will be i v. 
If we repeat the experiment with a ball of half the weight, ' 
and twice the velocity of A, striking B in free space, the 
effects will be very different. We must then have a longer cylin- ; 
der; for the length of it forced into the ball will be = 4 E ' 
and the velocity of both balls after collision will be 4 v. It is 
not easy to understand how these last effects can be produced ! 
by a force no greater than the first. 
g. It is argued that the mass into the velocity must be the 
proper measure of the force of a body in motion, because the I 
sum of the products of the various masses of any system of 
bodies into their respective velocities, is always the same in the H 
same direction, unless acted upon by some external force. In , 
other words, because the motion of the centre of gravity of ' 
any system of bodies cannot be changed or disturbed by any in 
action of those bodies upon each other. j 
If two equal non-elastic balls A and B, whose common jti 
centre of gravity is G, (fig, Q.) move with the velocities and in 11 
the directions A C and B C, oblique to each other, they will b 
meet at C, and'after collision they will move on together with i 
the velocity and in the direction G C, If the product of the I 
mass. into the velocity in the same direction be taken as the > 
measure of the moving force, we have in the motion of these u 
bodies equal effects of force before and after collision. But it J 
is obvious, that to produce the separate motions of A and B 
before collision, much greater force must be required than to i 
produce the motion of their joint mass, 
(To be continued.) 
