Alma record. (Alma, Mich.) 1878-1928, 1894-04-13
The following criticism appeared in the
Moderator Of Jan. Is, 1884,
Kinetic Kick

ITHACA, Mich, December "a, 1893.
Editor Moderator:
Allow me, through your columns, to offer
some criticisms on the article in your issue
of December 81, entitled, Summary Of
Kinetics. II, - by Z. A. Slater of the Fenton
Normal. The multiplicity of terms used by
Mr. Slater in his chart and discussion would
be the means of involving all students. except
those who are unusually apt in mathematical
analysis. in ineXtricable confusion. His
terms, "ortos, ticks, ulta, vim," are worse
than useless. They serve no purpose in solu-
ton, and serve only TO confuse the pupils
ideas on the subject.
Again, he applies the law of uniformly
accelerated motion TO problems which can
only be solved by laws governing variably
accelerated motion, "a In problem i. In
this problem he assumes that the pressure
on the ball Ia uniform from breech to muz-
zle of the gun. The law cannot be stated
exactly, as il varies with the granulation of
the powder, the finer the granulation the
nearer the approach TO instantaneous burn
ing. Surprising the powder to burn instan-
taneously, il thus being changed to gas be-
fore the ball starts on its journey, the pres
sure would be inversely as the distance of
the ball from the breech, until it reaches the
muZzle.
give herewith a simple development of
the laws of uniformly accelerated motion
II We divide an infinitely small portion of
the space by an infinitely small portion of
the time, we have the velocity at any time,
which is variable quantity. Hence, we
DIS
may assume W But,ia the motion
dt
is uniformly accelerated, we have Il.
where represents the accelerating force.
Combining these equations we have d g. IT
d {. migrating, we have 8 - # square
plus C, where G represents a constant. Sup
posing The initial or final velocity to be zero,
the equation and others derived by combin-
ing il with - TT We can solve every problem
of uniformly accelerated motion. The
three equations most used are So #; s
vsquare
- II square; - -.
In these represents total space, the time
in seconds, the velocity and the accelerat-
ing force.
Where questions of work are involved we
must add another element, IN, or mass,
usually reckoned in pounds, rs the force Of
gravity Is the most convenient means of
measuring mass; also e. energy, represent
ing work done, in English works represent.
ed in foot pounds, the unit being pound
falling freely through one foot of space.
m vsquare
The formula for energy Use - -
2g
the velocity produced by gravitation on a
body starting from rest and falling freely
for one second of time. This value at the
sea level in latitude of 45o is approximately
81 1-6 feet. This formula for energy with those
of motion before given are sufficient to solve
all problems of work in which constant or
invariable forces are involved.
The dyne and erg are units of force and
work, respectively used in French works in
the place of z and the foot pound; the pupils
mind, should, however, he impressed with
the fact these are other units for measuring
the same thing, just IA the meter and gram
are other units for measuring length and
weight.
Another distinction which should be i'm
pressed on the pupils mind, seemingly
entirely ignored by Mr.. Slate, is that upon
which depends the measure Of force and the
measure of work.
Forces are proportional to the moments
produced by them in equal times.
IhNi is. nv for = given time represents
toe measure of force, while NV square rep
reseuLs he amount of work or energy in a
-1v,r r,sss at given velocity, but in
uaiss i-oz snose vi gravity units. These units
are frequently used in disc ssion for sim
plicity, as they eliminate z (j2 Icy, which
enters all cases alike. The unit Of work is