FRICTION. 
<0 a weight arawiig ‘the: boy backwards on a Buel 
plane, or acting z contr das to the. ‘moving force, is equal t 
1 M x W 
3 where Mi is. the-. moving force ex- 
preffed by its ee W the — of the body upon the 
horizontal plane, the fpace through which the moving | 
a orce or weight = ded in che time ¢ F expreffed in feconds, 
61, 1 fee ae meafure i aed force of gravity. 
n increafes ma lefs 
w hen it has different furfaces applied to the plane. o 
it moves, but that the {malleit fanfaces will coe ve the leait 
friGion. To the experiments inftituted by Mr. Fergufon 
and others, from which conclufions have been drawn fo dif-- 
heen from thefe, Mr. Vince makes the following ae 
‘tions 3 it was their objet to determine what moving 
would ju/? put a body at reft in motion ; and having, a ae 
thought, Gn they thence concluded, that the accelera- - 
tive force was then ¢ equal to the friction. - But it is mani- 
feft, as Mr. Vince eae. 2 any force which will put a 
body’ ‘in motion muft be. greater than. the force which o 
pofes its motion, otherwife. it “would not overcome it $ and.: 
hhence, if there were no other objeétion but this, it is evi-. 
dent that the friftion could not be very accurately obtained. 
of 123 0% V 
nts: rft, a body 
plane, and then loaded with a at of 8lb. amd rae a 
moying ieee was applied as would, when the. body. was jue 
2 at ere without any pee eta 5 
in which i the friGtion muft be juft equal to the accelera- 
tive | aia ly was a fto beer when ita appeare ie 
that the fame moving force which had fe ept t 
before, would not put. it in motion, and it was found neceffa- 
ut mmotio: 
ry. to take.off, 45 oz: from the body before the fame moving. 
whence it pitied that this 
force would put it in motion.: 
‘bedy when laid upon the plane, at reft, acquired. a ver 
PP 
cated the cohefion was in proportion to. the friction when. 
it being, in the. latter cafe, , alent 
t ody hae in motion : 
one rd, a 
tt was found to be very 
fter all in ale we mutt 'r ur to ie ee 
and } reafonin of M. Coul omb._ for, a See and fatisfaQo- 
‘ry view of this complicated. lve of mechanical eo Sp 
ith 
His experiments, were condu¢ted, -on a large fcale, wi 
Tange. bodies and heavy. weights, fo that he. was: thus enabled. . 
t.only to corre€ the errors which un avoidably , arofe. from’ 
ae limited experinng ts of preceding writers, but to difpoyer-- 
new pheno mena, hile he confirmed. o er canelufons ; 
had before Been attally eftablithe Ve all here “aval 
eurfelves of the refilts of ‘his spiaaces as = ‘are pre 
eftroys the ; 
fented in an abridged Fos to the an by Di. Brewffer i int. 
"his edition of id ered s Mechanics, vol. 11. and refer for a. 
uller one the “ Journal cm Phyfique”’ for Sept. and. 
O&. 1785, ay XXVil. Pp. 206—282, Kc. 
1. The fri€tion of Homogeneous bodies, or’ bodies-of the 
fame kind moving upon one another, is generally fuppofed to 
be greater than that of heterogeneous bodies. 
opinion of Mufche nbroek, Krafft, Camus, and Bo 
Coulom 
found, for example, that the fri€tion of oak upon oak was ee 
1 : of the force of preffion 3 the fri€tion of pine againit 
The fri€tion 
pine was , and of oak againft pine = 
I 
1.78 
of oak againft copper was ree and that of oak againft 
iron aes the fame. 
. It was generally fuppofed, that in. the cafe of wood, 
Then 
the —_ moved in the direGtion of their fibres the friction - 
.of the. fibres with which they were preffed to- 
was: 
ee, ; but when the motion was  bontrany to the courfe of - 
ca 
. The longer the rubbing furfaces 2 remain in- contadt 
_ fri€tio tis is mentioned: by - 
canique,.§ 3 oulo 
the fibres, the fri@tion was only 
; but. mb has the serie 
of having eftablifhed the fate. Oo When wood was moved upon. 
ecording to the direction of the-fibres, the friGtion 
ood, a 
_ Was increafed by keeping the furfaces in. conta&t for.a few fe- 
. ed to: a minute, the. 
onds ; and when the time was. pro rolonge 
oe feemed to ane reached its fartheft = 
the. motion was performed contrary to the: 
res, a aad oe was necefiary before the fine 
at its maximum. ‘When wood. was: pea wpon, me ail . the 
in co 
time requifite for producing the greateft quantity. of friGion 
_is increafed. e increafe ] esas which is > generated by 
y 
prolonging the time . contact is: fo great, that a-bod 
' weighing. 1650 pounds: was moved. with a os of: 64. | 
pounds “when firfk aid 0 se its correfponding furface. After 
havin ng ears in contact for-. 
when. the: - 
" require it it in motion; an 
was cecsiges to fix days, it-could {care ely be moved wi . 
force of 622 pounds. When the-furfaces, ‘er metallic ba 
ther, the: ti reducing a 
gveafe:as an unguent, and was prolon: nee ed t 
b seni the. furfaoes with tallow 
4 pou ‘and oe oa 
was. Auccellively: a ee re the’ foes of 
‘2: CG 2.16 2.21 jis 
preffion ; 
a Aiba the - 
sacs did r not attain its maximum. till the furfaces: continued - 
tadt for' days ; and it. is: very remarkable, . 
’ that when wooden furfaces:-were anointed, ee -tallows. the. 
the {pace. of: cade feconds,. it . 
e 
