Moving Force. 121 
of A; and we shall then have three masses 
besides A, each equal to A, moving with half 
the original velocity of A, and all of them 
deriving their motion from the original force 
of A. 
8. Let A (fig. 8.) be a non-elastic soft mass, 
uniformly penetrable by the cylinder c; that 
is, the tenacity of the parts of A shall be such, 
that c shall meet with the same resistance at 
every point of its progress. Let A move with 
the velocity v, in the direction AB, against 
an immoveable obstacle, and be brought to 
rest by forcing the length EF of the cylinder 
into the ball. ‘That penetration of c¢ is, in this 
instance, the whole effect produced by the 
force of the motion of A. Let the operation 
be repeated, but instead of an immoveable 
obstacle, let B be a mass equal to A, in free 
space, but not penetrable by c: then the cy- 
linder will be forced into A a depth equal only 
to EF, and when the side of A has arrived 
opposite to H, the side of B will have arrived 
opposite to I, (as represented at No. 2.) and 
the velocity of both balls will be iv. 
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- 
Q 
