264 Remarks on the Central Forces of Bodies 
in the circle can have no influence upon the deflecting force. 
But a body moving in a curve or circle is always found to be act- 
ed upon by a third force, which is opposite and equal to the de- 
flecting or centripetal force; and as there cannot be an effect 
without a cause, this third force must either be derived from one 
of those mentioned above, or their resultant—or from some other 
source. Supposing the circle BD, in which the bar moves, to be 
one foot in diameter and the velocity of the bar to be 25.14 feet 
per second, or at the rate of eight entire revolutions in a-second, 
wv? 25.14? 
its centrifugal velocity would be=5-= 7 =632 feet per se- 
cond, and its centrifugal force =39 lbs. its weight being one pound, 
v representing the velocity in the circle, and r its radius; for if a 
be the weight of the bar, g equal to 32, feet, and x the ‘force re- 
: ees re 25.142 7 f 
quired, then, r 3 eae : Pred 16 = 39 lbs.* But the force 
25.14 
in the circle= 46° =1. 55 lbs. only, consequently the centrifu- 
gal force could not have been caused by the projectile force. And 
it is evident that it cannot be a part of the magnetic force, for it 
acts in a directly opposite direction ; and it is equally evident that 
it cannot be the resultant of the other two forces, for then its di- 
rection would be to some point within the circle. The pressure 
from the centre of thirty-nine pounds must therefore have origin- 
ated in some other way. 
Such are. the facts when the deflection from a straight line is 
caused by a centripetal force directed to a fixed centre of rota- 
tion, and the projectile or moving force is applied before the body 
is constrained to move in a circle. We will now stop the revolv- 
ing rod r, leaving the bar A attached to m, by the magnetic force, 
If by means of a winch the same number of revolutions in a 
second be given to the bar that it had in the first experiment, the 
centripetal or magnetic force will perform the part of cohesion, 
and the circumstances in every other respect will be the same 
that would attend such a rotation if the bar were welded to 1. 
st ae 
or, in other eee is centrifugal force a part of the force anes 
= tor canal ? ee attempting to prove the nega- 
© Pies i tee gag ET 
1G ’s Mechanics. 
ee : oe 
