South Bend news-times. (South Bend, Ind.) 1913-1938, 1918-05-01
Natures GRADUATION Magic
BY GARRETT p. SERVISS.

A reader who accepts the Cali
lean law that all bodies fall under
the action of gravity at the same
speed, without regard to their
weight, is puzzled by an experiment
of his own. which he thus describes:
why. if the law holds good Of all
bodies acted upon by grdvitation,
does a man weighing zoo pounds
come down hill, cOasting on BIZ
cycle faster than one weighing
only $50 pounds? At first l thought
il might be due TO the easier run
ming Of the heavier mans ma
chine, but on exchanging machines
the contradiction of Galileo's law
proved to be positive"
The inquirer's statement of the
law is not quite accurate. and there
from arises the interesting paradox
that troubles him. The law is that
all bodies fall under the action of
gravity at the same velocity pro-
vided that there is no resistance.
The friction of the air furnishes re-
sistance and when the bodies are
light this resistance may greatly
diminish the velocity.
But when the bodies are dense
and heavy the air resistance may
be disregarded. except for purposes
of exact experimentation.
Thus. Calico disregarded the air
resistance i'm his celebrated ex-
pertinent Of dropping cannon balls
from the leaning tower Of Pisa.
The balls, although one weighed
10 pounds and the other only one
pound. struck the ground stimuli
taneously. as far as sight and hear
ing could determine, after a vertical
fall of say $50 feet. Being both of
the same dencity, the surface OF the
larger must have been about 4.6
times greater than that Of the
smaller. but on the other hand. its
momentum was ten times greater
which more than sufficed 20 over
come the increased resistance due
TO the larger surface. To demon
strate the law strictly the expert
ment should be tried in a perfect
vacuum There a grain OF dust. or
feather would fall as swiftly as
marble or "A lead bullet.
Now. 10 understand the case of
the coasting bicycles. we must re-
member that there are two ways
OF measuring the effects Of gravity
The ordinary way is TO estimate it
BY the weight that il imparts TO
body Gravitation is a force that
acts equally upon all the particles
making up body. If there are
many such particles the body is
heavy under the pull OF gravity;
if there are few. it is light.
II a heavy and a light body are
set i'm motion with the same velocity
the heavy one will have more mo-
mentum (velocity multiplied by
mass. or weight) and consequently
more ability 10 overcome resistance
and 10 strike a heavy blow.
But when we are dealing with
falling bodies, or bodies that get
their motion solely from the force
OF gravity. we disregard the weight
and consider only the velocity. be-
cause tie velocity impaired by
gravity the same FOR ali bodies,
indepen Of their weight. Yet
when n are once in motion. II
there is any resistance. like that
OF the air, 20 be overcome. the
heavier body will. in certain circum-
stances. get ahead
Suppose. for instance, that two
small bodies II the same size. but
one weighins. 100 times as much
as the other. are let fall together
from a great height. They will
start at the same speed and for
short time will gain velocity at
the same rate: hut since the re-
sistance OF the air increases with
the velocity the light body will
soon begin 10 be retarded. because
II Is less able 70 overcome the re-
sistance II il is very light IL may
he arrested while the other goes on.
There would be a similar result
II the two bodies were OF the same