\ 
268 Remarks on the Central Forces of Bodies 
site direction with the same velocity.”* The force applied to 
the winch, in the case above, was wholly expended in giving ve- 
locity to the rim, with the slight exceptions mentioned. Conse- 
quently, whatever other forces may have operated on the rim whilst 
revolving must have originated in some other way. And yet those 
extraneous forces would amount to 1480 lbs., as shown by the above 
formula, the rim weighing 150 Ibs. and being revolved at the rate 
of two entire revolutions in a second. No part of this force could be 
communicated to the arm of a man who would stop such a wheel 
by seizing one of the spokes, because each particle of the rim isact- 
ed upon by the central forces, which are al ways opposite and equal, 
in the direction of the radius of the circle at that point ; and it 
has just been shown that the moment of rotation of each particle 
is equal to the moment of rotation of the power that impels it, 
but “as the direction of the central forces is in that of the ra- 
dius, their moment of rotation is equal to nothing.”+ Conse- 
quently the centrifugal force cannot act upon the hand that stops 
the wheel. If, indeed, the centrifugal force were increased to 
sixteen times the above amount, the result would be the same. 
By giving the wheel eight revolutions in a second we would have 
the central foree= 1480 x 16=23680 lbs. and the force in the cit- 
12.57 x8 x 150 
cle would be = 925 lbs. Here the centrifugal 
force is twenty times greater than the force in the circle, and yet 
as the central force would act in the direction of the radii, its 
moment of rotation would be=0, Or, what is more strictly the 
fact, the central force acts by pressure, and a resultant from that 
pressure and the force in the circle is the consequence, but so 
long as resistance from cohesion continues, neither motion nor 
pressure can be imparted to another body by the central foree. 
These are the obvious reasons why no greater force could be 
communicated by the rim than the 925 lbs., which it only pos 
sesses as a mass of matter moving in a circle. 
The following experiment may be considered as 2 practical 
illustration of the theoretical views given above. A whirling 
table may be made of any convenient size, we will say, for the 
-Present occasion, rather more than four feet in diameter, to revolve 
horizontally on friction rollers placed near the center ; the axle 
being a hollow cylinder, through which four cords pass to the 
“© Ester and Lardier on Mechanics, p. 24. : 
t Renwick’s Mathematics, Art. Composition of Forces. 
