The Traffic Accident Reconstruction Origin -ARnews-

Re: 360 DEGREE COUNTER-CLOCKWISE LINEAR MOMENTUM

Ed Livesay (elivesay@alltel.net)
Sun, 15 Jun 1997 09:27:06 -0400 (EDT)

Jim:

There are two systems in use which are based upon the "Cartesian Coordinate Grid"
(compliments of Rene Descartes of Newton's era). Some employ the "Right-hand"
coordinate system and others employ the "left-hand" system of measurement. Most
of us in the recon world use the left-hand system (Daily's momentum method is
a classic example). SAE conventions use the right-hand system (as does the EDVAP
software series and others).

Even though there are some slight variations, the left-hand system mandates that
angles be measured counter-clockwise with zero degrees being found at the "3-O'Clock"
position and the X-axis being the "flat" or horizontal axis. The right-hand
system, more often than not, has the X-axis as being the "up and down or vertical" axis
and angles being measured from a clock-wise perspective.

Conversions from one system to another can be done but are tedious. Seems like there
is an article in either the Accident Reconstruction Journal or the Quarterly about
the topic.

I've not seen the right-hand system being used for momentum problems in a 360-deg setup though.

Ed Livesay
elivesay@alltel.net

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