Conservation of Momentum Analysis of Two-Dimensional Colliding Bodies, With or Without Trailers

This paper presents a method of automobile collision analysis based on conservation of momentum. The analysis is applied to the collision of two two-dimensional bodies, either or both of which may be attached to a trailer.

Newton's laws of motion are employed to determine changes in linear and angular velocities for the two-dimensional colliding bodies. Knowing the masses and rotational inertias and the initial velocities of all bodies at impact, the post-impact velocities can be calculated if appropriate constraints are applied to the bodies' post-collision motion. Various motion constraints, including lock-up, slip, and restitution are examined, and a methodology for modeling vehicle motion experienced during a collision is presented. The full set of basic equations characterizing this conservation-of-momentum analysis is presented with sufficient detail to allow their implementation on a programmable calculator or personal computer.

A Windows™-based computer program written to implement the method is introduced. Called PLASMO, the program's accuracy is briefly examined by comparison to previously published reconstructions of instrumented crash tests.