= ’ 
al 
Moving Force. 123, 
greater force must be required than to produce 
the motion of their joimt mass. 
10. If two elastic equal balls E and F, 
(fig 10: ) mov ing with the respective velocities 
AC and’ ‘AB, at right angles to each other, 
strike at the sameiastant a third elastic ball 
A, equal to E or F; E and F will be brought 
to rest, and A will move off with the velocity 
and ‘in the direction AD. In this case, the 
whole amount of the forces of E and F must have 
been communicated to A; but the velocity 
acquired by A is less than the sum of the velo- 
cities of E and F. 
(1. if the directions of E and F be not at 
right angles, (as in fig. 11. ) the result will be 
as follows: produce AB, and draw the per- 
pendicular DG. After the str oke, the velocity 
2AB x AD 
of A in the direction A B, will be ~ AB LAG» 
and E and F will each: continue to move in 
AB x BG* 
B+ AG. 
In his case, as in all alias the velocity and 
the direction of the centre of gravity of the 
system is, no doubt, the same before and after 
their fir st directions with the Vv elocity 3a AG a 
* If BAC be an obtuse ‘angle, the same solution applies, 
enly 2 aad F rebound instead of proceeding forward. 
Q2 
