FORCE. 
This {pecies of force has been, fir by edie - af- 
terwards by seanioog a very aptly denominated mechanic 
e of ee ee is mean ee se 
tity of mechanic force ‘pollefled by a body in motion to be. 
eftimated by its quantity of mechanic effect, I apprehend 
that it cannot be contr overted, that it is in hie eee to the 
y jointly. 
But of this quantity « of force Newton no w where treats, 
and has accordin ngly 8 n no eens on of it fter de- 
,a 
fining what h ay the guantitas aceleatris and guan- 
titas motrix, he had had se ceae to convey an equa 
tinét idea of the quantitas mechanica, feuleay from the con- 
tinued action of any force, he might not improbably have 
proceeded conbemal ly to the definition given a Smeaton, 
and have added, * quantitas mechanica eft menfu a propor- 
tionalis {patio per quod data vis pena exerci 3” ors . 
peaking with ae to the accumulated energy comm 
d to a bod 
nicate 
citatis quam in dat oc 
Bat if we attend to the fie ‘ords of his preface to the 
firft edition of his “ Principia,’’ he evidently had no need 
of fuch a definition ; ** Nos autem non artibus fed philofo- 
phice confulentes, deque potentiis non in manualibus fed 
naturalibus {cribentes,’? &c. and 
effet in the fc 
“¢ Ceterum mechani 
erg 
— “ propor ionalis dusdaes an 
orpore 
motion; 
icam tra€tare non eft hujus initituti.”” 
Dr. Wollafton proceeds to obferve, that if it be of any real 
utility to give the name of force to this complicated idea of 
wis motrix pe iraae through time, as well as that of momen- 
s when unrefilted, it would “— requifite to dif- 
ne this force, always by fone uch appellation as mo- 
orce 5 for it is to be apprehended, that, for want of 
ion, many writers themfelves, and it is certain, 
that many readers of difquifitions on this fubje&, have con 
founded and compared together vis motrix, momentum, on 
vis mechanica; quantities, that are all of them totally dif- 
fimilar, and bear no more comparifon to each other than 
lines to furfaces, or furfaces to folids. 
In practical mechanics, however, i it is, at leafk very rarely, 
f bodies is in any degree an obje of 
eee cae velocities given by different quantities of 
eietis force to bodies of equal or unequal magnitude, 
have been fo diftinétly aoe of by Smeaton, (Phil. Tranf, 
vol. 66. p. 450.) in a feries of moft direct experiments, 
that it would be a needlefs waite of time to re-confider them 
on the contrary, the quantities of 
sa moving 
f impetus, 1as clearly 
traced by t me accurate eee imei Ga 72.p.337 7) 
But cae. is one view in which the comparative — 
orce,) is always equal to that from which it originated. 
As the fimpleft cafe of entire transfer, the body A may 
be fuppofed to af upon B in a dire& line, Gach the me- 
: Vv. 
dium of a light {pring, fo contrived, that the {pring is pre” 
vented by aratchet from returning in the direGion towards 
A, but expands again entirely in the. direCtion towards B, 
and by that means exerts the whole force which had been 
wound up by the action of A in giv ing | motion 
a this cafe, fince the moving forc the {pring is ile 
acting 
ce) t 
fimple ee le ratio of the pene a ane arene 
e lu 
ure by t 
plicate ee of the bodies employe ed; and i 
w oo capable of reproducing ‘etl aaa 
re) eos ictio 
tude, ce eee force acquired 
euale might be ed in counteraGting the ufual refift- 
ances, and perpetua ioe would be effected. But fince 
the impetus remains unaltered, it is evident that the utmoft 
which the body B ee effeét in return, would be the re- 
production of A’s velocity, and reftitution of its entire me« 
chanic force, neither cage nor cai cps by 
the pacar imperfection of machin he ility 
of perpetual motion is, reat eres “Gaol with 
thofe panels which meafure the quantity of force by the 
quantity of its extended effe&t, or by the fquare of the ve. 
locity which it can produce. 
In eftimating the utmoft ‘effe& which one body can pro« 
duce upon another at reft, the fame refult is obtained a 
employing impetus as sfoenfional ome according to * 
ens; for if the bedy A were allowed to afcend tot ie 
height due to its velocity, an if, by any eae mechani- 
cal centrivanee of a or otherwife, the body B were to 
‘ee raife the ea ‘of A, it is well known that the 
ights of. afcent would be reciprocally as the bodies; and 
Soalequectle that the /guare of the velocity to be acquired 
by free defcent of B would be in that ratio, and the quanti- 
ty of mechanic force would be preferved,as before, unaltered. 
It ma ay be of ufe oe to confider another application - 
re, 
“a 
5. 
which the body w 
would be reciprocally as Me eee we force, the angular 
motion of the lever and {pace throug which the {pring 
bend would be the 
acs 
{pria 
fa pion to it-t 
may be Soaeer ee. that the times in which thele 
total effects are produced may be varied at Len eer in aah 
the, 
centre of motion; and it thauld: not vals ay oe ‘ale 
bei 
tage 5 yet, 
the contrary, any quantity of mechani¢ see 1g -not able 
+ to 
