62 
MOVING FORCE. 
(liises of diffi- 
culty in till' 
doctriiK'<! of 
Hiovmg force. 
with many other practical men, in the application of the pre* 
vailing doctrines of moving forces ; in the hopes that others, 
better qualified for the task, may be prevailed upon to recon- 
sider the subject, and remove the obscurities in which some 
parts of it appear to be involved. 
I shall first briefly describe some particular cases where these 
dilficulties occur, divesting them as much as possible of all com- 
plicated circumstances; and I shall be careful to state such 
facts only as will be readily admitted by any one moderately 
acquainted with the subject. I will then quote, from approved 
W'riters on mechanics, such observations as appear to have been 
given in explanation of the points in question, accompanied 
with some remarks which they seem to require; and I shall 
conclude, by venturing to offer some farther explanations, 
which appear to me to be capable of general application iiv 
mechanics. 
Examples of Force producing Motion in Bodies from a Slate'' of 
Rest. 
A 
1. If two balls, A and B, (figure 1.) whose masses are as 1 
to 4, be suspended like pendulums ; and if they be set in 
motion by two equal weights, C and D, acting on them by 
means of the bent levers, E and F, whose fulcra are fixed, and 
whose perpendicular arms are equal, but the length of the hori- 
zontal arm of F, twice the length of the corresponding arm of 
E. If C descends through the space S, D will descend through 
an equal space in the same time ; and by these equal forces in 
equal times, A will have acquired exactly twice the velocity of 
B. J\ow if these effects are to be measured by the products of 
the masses into their velocities, D produces twice the effect of' 
C, although their forces are precisely equal. 
Ill this and the following cases, the mass of the lever, &c. is' • 
supposed to be indefinitely small, when compared with that of 
the ball which it moves. 
2. If we suppose two balls, m and (fig. 2.) whose masses 
are as 1 to 2, to be suspended as in the last case, and put in 
root ion.. 
