Direcr Rrapinac ACCELEROMETERS. 
By C. R. Moore. 
Every person is more or less familiar with the subject of acceleration 
or deceleration 
changes of velocity—whether or not the laws governing 
the same or the mathematical expressions therefor are understood. Such 
everyday occurrences as passengers swaying to and fro partially suspended 
from street car straps, the hurry up that accompanies one’s movements as 
he tries to reach the car door just as the motorman stops the car, are 
examples which prove this. Changes in the rates of motion are essential 
to all forms of transportation, and the more rapidly a car or train can be 
brought up to speed (or stopped) the shorter will be the time required be- 
tween two points when a given number of stops must be made. Railway 
trains, street and interurban cars are therefore started and stopped as 
quickly as is consistent with reasonable comfort, in response to the demand 
of the traveling public for fast time. 
It is the purpose of this paper to discuss briefly the laws of motion, 
and to describe a new device for measuring the rate of change of velocity, 
showing results of tests recently conducted in the Electrical Laboratories 
at Purdue University. 
The author realizes at the outset that the subject of acceleration 
Ineasurement is an old one and is rather reluctant to lay claim before this 
body of scientists that what is offered herein is new. However as far as 
his knowledge goes this device has not been used previous to this time. 
The scheme is brought to your attention for whatever consideration it may 
merit. 
Before discussing accelerometers in detail, a brief study of just what 
is meant by acceleration and deceleration may be of value. 
In Fig. 1 curve “D” shows distances plotted against time, the dis- 
tances being taken as ordinates and the time as the abscissee. The car is 
to be thought of as moving from a certain point “O,” distances ‘‘d” being 
measured from that point at the end of the any time “td.” It will be noted 
that during the first few time units after the car starts the distance passed 
through each successive unit is greater than that passed through during 
the preceding unit of time, i. e. the rate of motion is increasing. At the 
