FORMULA FOR FINDING SPEED OF OBJECTIVE- 
BY 
LIEUTENANT F. BROWN, I.O.M., R . A . 
The following simple formula for finding speed of objective may ba 
useful to Garrison Artillery officers. 
Although simple, it possesses the merit of being accurate if the 
following condition is allowed, viz : the range—whilst the object is 
travelling over one degree—as constant. 
Let 
R = range in yards. 
t = time in seconds object is moving over one 
degree, measured by^D.R.F. 
v = speed of objective. 
Then 
v (in knots) = *031 . 1. 
v (in miles) = *0357 ~ . 2. 
I also forward small diagram, by which the same result can be 
obtained without calculation. The diagram hardly requires explanation. 
Examples :— 
(1.) Range 4,000 yards and object moves over one degree in 15 
seconds. Find speed ? 
Run the 4,000 yards range up vertically until it cuts the 15 second 
diagonal line ; then measure the length of this ordinate on the scale at 
the left hand side of diagram and this will give the speed of objective 
in knots per hour. In this particular case, the speed is about 8 # 25 
knots per hour. 
(2.) Range 4,250 yards and time taken to pass over one degree 
10 seconds. Find speed ? 
2. VOL. XXIV. 
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